Ex Libris C. K. OGDEN O F T H E I, AW S of C H A N C E, M E T* H O D Of Calculation of the Hazards of GAME, Plainly demonftrated, And applied to GAMES at prefent inoft in Ufe ; Which may be eafily extended to the mofl intricate Cafes of CHANCE imaginable. The FOURTH EDITION, Revis'd by JOHN HAM. By whom is added, A Demonftration of the Gain of the Banker in any Circumftance of the Game call'd PH ARAON ; And how to determine the Odds at the ACE of HEARTS or FAIR CHANCE ; With the Arithmetical Solution of fome Queftions relating to LOTTERIES; And a few Remarks upon HAZARD and BACKGAMMON. LONDON: Printed for B. MOTTE and C. BAT HURST, at the Middle- temple Gate in Fket-Jireet. M.DC c .xxx v 1 1 1 . ' [ail PREFACE. T is thought as neceffary to write a Preface before a Book, as it is judgd civ//, when you invite a Friend to Dinner, to proffer him a Glafs of Hock beforehand for a Whet : And this being maim'd enough for want of a 'Dedication, I am refolv 'd it fball not want an Epiflle to the Reader too. I fhall not take upon me to determine, whether it is lawful to play at *Dice or not, leaving that to be dtf- puted betwixt the Fanatick Parfons and the Sharpers ; / am fure it is lawful to deal with 'Dice as with other Epidemic *Diflemprs ; and I am confident that the writing a Book about it, will contribute ai little towards its Encouragement, 'as Flux- ing and 'Precipitates do to Whoring. A 3, It iv PR EF ACE. It will be to little purpofe to tell my Reader, of how great Antiquity the play- ing at T)tce is. I will only let him know-, that by the Alcae Lucius, the Antients com- prehended all Games, which were fubjec- ted to the determination of mere Chance ; this fort of Gaming was fir iff ly forbid by the Emperor Juftinian, Cod. Lib. 3. Tit. 43. under very fey ere Penalties', and Pho- cius Nomocan. Tit. 9. Cap. 27. acquaints us, that the Ufe of this was altogether denied the Clergy of that time. Seneca fays very well, Aleator quanto in arte eft melior, tamo eft nequior ; That by how much the one is more skilful in Games, by fo much he is the more culpable; or we may fay of this, as an ingenious Man fays of T)ancingi That to be extraordinary good at it, is to be excellant in a Fault ; there- fore I hope no body will imagine I had fo mean a ^ejign in this, as to teach the Art of T laying at A great part of this ^Difconrfe is a Tranflation from Monf. Huygen'j Treatife, De ratiociniis in ludo Alcse ; one, who in his Improvements of 'Philofophy, has but one Superior, and I think few or no K- quals. The whole I undertook for my own tDivertifement, next to the Satisfaction of foms P R E F A C.^E. V fome Friends, who would now and then be wrangling about the ^Proportions of Hazards in fome Cafes that are here de- cided. All it requir'd was a few fpare Hours, and but little Work for the Brain ; my T>efign in publishing it, was to make it of more general Ufe, and perhaps per- fuade a raw Squire, by it, to keep his Mo- ney in his ^Pocket -, and if, upon this ac- count, I fhould incur the Clamours of the Sharpers, I do not much regard it, Jince they are a fort of ^People the World is not bound to provide for. Ton willfnd here a very plain and eafy Method of the Calculation of the Hazards of Game, which a man may under ft and,with~ out knowing the Quadratures of Curves, the "Doctrine of Series's, or the Laws of Conccntripetation of Bodies, or the ^Periods of the Satellites of Jupiter ; yea, without fa much as the Elements ^Eu- clid. There is nothing required for the comprehending the whole, but common Senfe ana practical Arithmetick ; facing a few Touches of Algebra, as in the frft Three 'Proportions, where the Reader, without fufpicion of *Popery^ may make ufe of a ftrong implicit Faith ; tho I muft confefs^ it docs not much recommend it fclf to me in thefe Turpofes ; for / had rather he would vi PREFACE. would enquire, and I believe he will frid the Speculation not tinpleafant. Every mans Succefs m any Affair is proportional to his Conduct and Fortune. Fortune (in the fenfe of moft f People}Jig- wfies an Event which depends on Chance^ agreeing with my Wi$\ and Misfor- tune fignifies fuch an one, whofe imme- diate Caufes 1 don't know, and consequently can neither for et el nor produce it (for it is no Here/} to believe^ that Providence Buf- fers ordinary matters to run in the Chan- nel of fecond Caufes}. Now I fuppofe, that all a wife Man can do in fuch a Cafe ts y to lay his Buftnefs on fuch Events, as have the moft powerful fecond Caufes, and this is true both in the great Events of the World, and in ordinary Games. It is impojfible for a , with fuch deter- mirid force and direction, not to fall on fuch a determined fide, only 1 don't know the force and direction which makes it fall on fuch a detennirid Jide, and there- fore I call that Chance, which is no- thing but want of Art -, that only which is left to me, is to wager where there are the greateft number of Chances^ and confidently the greateft probability to gain -, and the whole Art of Gaming, where there is any thing of Hazard, will be PREFACE. vii fie r edited to this at lafl, viz, in dubious Cafes to calculate on which fide there are moft Chances j and tho' this can't bt done in the mid ft of Game precifely to an Unitj yet a Man who knows the 'Principles ', may make fitch a conjecture, as will be a fuf- fcient direction to him ; and tho' it is pof- fible, if there are any Chances againft him at all, that he may loft, yet when he chufith the fafeft fide> he may fart with his Mo- ney with more content (if there can be any at all] in fitch a Cafe. . I will not debate, whether one may en- gge another in a disadvantageous Wager. Games may be fupposd to be a try at of Wit as well as Fortune, and every Man, when he enttrs the Lifts with another^ unlefs out of Complaifance, takes it for granted^ his Fortune and Judgment, are, at Icaft, equal to thofe of his *P lay -Fellow; but this I am fure of, that falfe Dice, Tricks of Lcger-dc-main, &c. are inex- cufable, for the queftion in Gaming is not y Who is the heft Jnglcr ? The Reader may here obferve the Force of Numbers, which can be fuccefsfully ap- plied, even to thofe things, which one would imagine are fubjett to no Rules. There are very few things which we know y which viii PREFACE. which are not capable of being reduced to a Mathematical Reafonmg-, and when they cannot , it's a fign our Knowledge of them is very fmall and confus'd 5 and where a mathematical reasoning can be had, it's as great folly to make life of any other, as to grope for a thing in the dark y when you have a Candle flanding by you. I Relieve the Calculation of the Quantity of 'Pro- bability might be improved to a very ufe- ful and pie af ant Speculation, and applied to a great many Events which are acci- dental, befides thofe of Games ; only thefe Cafes would be infinitely more confused, as depending on Chances which the mo ft part of Men are ignorant of-, and as 1 have hinted already, all the Politicks in the JVorld, are nothing elfe but a kind of Ana- lyfis of the Quantity of probability in cafual Events, and a good 'Politician (ig- Tiifies no more? but one who is dextrous at fuchCalculations ; only theTrinciples which are madeufe of in the Solution of Juch J'ro- blems^ cant be ftudied in a Clofet, but ac- quir'd by the Obfcrvatien of Mankind. There is likewife a Calculation of the Quantity of 'Probability founded on Ex- perience, to be made ttfe of in JVagers a- bout any thing ; it is odds> if a Woman is with PREFACE. be with Child, but it fhall be a Boy 5 and if you would know the juft odds, you muft confider the 'Proportion in the Bills that the Males bear to the Females : The Tearly Bills of Mortality are obfer c u t d to bear fuch ^Proportion to the live People as i to 30, or 26 ; therefore it is an even Wager y that one out of thirteen, dies within a Tear (which may be a good reafon, tho not the true, of that foolifi piece of Super- Jlitiori], becaufe, at this rate, if i out of 2.6 dies, you are no lofer. It is but i to 18 if you meet a Parfon in the Street , that he proves to be a Non-Juror, becaufe there is but i of $6 that are fuch. It is hardly i to 10, that a Woman of Twenty Tears old has her Maidenhead, and almoft the fame Wager, that a Town -Spark of that Age has not been clap'd. / think a Man might venture fome odds, that 100 of the Gens d'arms beats an equal Number of Dutch Troopers; and that an Englifh Regiment ftands its ground as long as ano- ther, making Experience our Guide in all thefe Cafes and others of the like nature. But there are no cafual Events, which are fo eafily fubjeffed to Numbers, as thoft of Games ; and I believe, there the Specu- lation might be improved fo far, as to bring in the Doctrine of the Series'.? and Loga- a rithms. x PREFACE. richms. Since Gaming is become a Trade, 1 think it ft the Adventurers fiould be upon the Square ; and therefore in the Con- trivance of Games there ought to be aftrift Calculation made ufe of] that they mayn't put one Tarty in more probability to gain than another ; and likewife, if a Man has a conjtderable Venture ; he ought to be al- low d to withdraw his Money when he pleafes, paying according to the Circum- Jtances he is then in : and it were eafy in moft Games to make Tables, by Infpeffion of which, a Man might know what he was either to pay or receive, in any Cir- cumjlances you can imagin-, it being conve* Silent to fave apart of ones Money, rather than venture the lofs of it all. I fa-all add no more, but that a Ma- . thematician will eajily perceive, it is not .put in fuc h a Drefs as to be taken notice oj by him, there being abundance of Words fpent to make the more ordinary fort of 'People under jland it. FOR the fake of thofe who are not vers'd in Mathematicks, I have added the following Explanation of Signs. = Equal. 4- More, or to be added. Lefs, or to be fubtra&ed. x Multiplied. -f- Divided. EXAMPLE.' 3 x4-f- 3 i = i4 = |tf, is to be read thus $ 3 multiplied in 4, more by 3, lefs by i] is equal to 14, which is equal to five ninth parts of a. An EXACT METHOD For S O LV I N G the HAZARDS of G A M E. LTHO' the Events of Games, which Fortune folely governs, are uncertain, yet it may be certainly determin'd, how much one is more ready to lofe than gain. "For Example: If one mould wager, at the firft throw with one Die, to throw fix, it's an accident if he gains or not ; but by how much it's more probable he will lofq than gain, is really de~ termin'd by the Nature of the thing, and capable of a ftricl: Calculation. So likewife if I mould play with another on tfyis con- dition, that the Victory mould be to the three nrft Games, and I had gain'd one al- B ready, 2 Solution of the ready, it is flill uncertain who mall gain the third j yet by a demonftrative Reafon- ing, I can eflimate both the Value of his Expectation and mine, and confequently (if we agree to leave the Game imperfect) deter- mine how great a mare of the Stakes belong to me, and how much to my Play-fellow ; or if any were defirous to take my place, at what rate I ought to fell it. Hence may arife innumerable Queries among two, three, or more Gameflers : and lince the Calcula- tion of thefe things is a little out of the common Road, and can be oft-times apply'd to good purpofe, I fhall briefly here ihew how it is to be done, and afterwards ex- plain thofe things which belong properly to the Dice. In both Cafes I fhall make ufe of this Principle, Ones Hazard or Expectation to gain any thing, is worth fo much, as, if he had it, he could pur chafe the like Hazard or Expectation again in a jujl and equal Game. For Example, if one, without my Know- ledge, mould hide in one hand 7 Shillings, and in his other 3 Shillings, and put it to my choice which Hand I would take, I fay this is as much worth to me, as if he mould give me 5 Shillings ; becaufe, if I have 5 Shillings, I can purchafe as good a Chance again, and that in a fair and juft Game. PRO- HAZARDS of Game. 3 PROPOSITION I. If I expett a or b, either of which, with equal probability ', may fall to me, then my Expectation is worth *t- y that is, the half Sum of a and b. THAT I may not only demonflrate, but likewife invefligate this Rule, fuppofe the Value of my Expectation be x-, by the former Principle having x, I can purchafe as good an Expectation again in a fair and juft Game. Suppofe then I play with another on thefe terms, That every one flakes x, and the Gainer give to the Lofer a, this Game is juft ? and it appears, that at this rate, I have an equal hazard either to get a if I lofe the Game, or 2x^-a if I gain ; for in this cafe I get 2X, which are the Stakes, out of which I muft pay the other a ; but if 2x a were worth k 9 then I have an equal hazard to get a or b ; therefore making 2x ==^, #== 7-' which is the Value of my Expectation. The Demonstration is eafy ; for having a ^ , I can play with another who will flake ^~- againfl it, on this condition, that the Gainer fhould give to the Lofer a; B 2 by 4 Solution of tie by this means I have an equal Expectation to get a if I lofe, or b if I win ; for in the laft cafe I get d-\-b the Stakes, out of which I muft pay a to my Play-fellow. In Numbers : if I had an equal hazard to get 3 or 7, then by this Proportion, my Expectation is worth 5, and it is cer- tain, having 5, 1 may have the fame Chance ; for if I play with another, fo that every one flakes 5, and the Gainer pay to the Lofer 3, this is a fair way of gaming j and it is evident I have an equal hazard to get 3 if I lofe, or 7 if I gain. PROP. II. IJ I expett a, b, ore, either of which, 'with equal facility ^ may happen ^ then the Value of my Expectation is - H , or the, third part of the Sum of& 3 b, and c. FO R the Inveftigation of which, fup- pofe x be the value of my Expecta- tion j then x muft be fuch, as I can pur- chafe with it the fame Expectation in a jufl Game: Suppofe the Conditions of the Game be, that playing with two others, each of us flakes x, and I bargain with one of the Gameflers, if I win, to give him b, andrhe fhall do the fame to me 5 but with the. HAZARDS of Game. 5 the other, that if I gain, I (hall give him c > and vice versa ; this is fair play : And here I have an equal hazard to get b y if the firft win, c if the fecond, or 3 AT c if I gain myfelf ; for then I get 3*, viz. the Stakes, of which I give the one b and the other c ; but if 3* b c be equal to a, I have an equal Expectation of a, b y or c therefore making 3* b c = a, t which is the Value of my After the fame Method you will find, if I had an equal hazard to get a, b y c, or d, the Value of my Expectation + +c + tl y that is the fourth part of the Sum of a, b t c, and d, &c. PROP. 6 Solution of the PROP. III. y the number of Chances, by which a falls to me, be p, and the number of Chances, by which b falls, be q, and fuppofing all the Chances do happen with equal facility, then the Value of my Expectation is lii q 5 i. e . the Product of a multiplied in the number cf its Chances added to the Product of b, multiplied into the number of its Chances, end the Sum divided by the number of Chances both of a and b. SUppofe, as before, x be the Value of my Expectation ; then if I have x, I muft be able to purchafe with it that fame Expectation again in a fair Game : For this I mall take as many Play-fellows as, with me, make up the number of p -f- q, of which let every one flake x, fo the whole Stake will be px 4- qx, and every one plays with equal hopes of winning ; with as many of my Fellow- Gamefters as the Number q ftands for, I make this bar- gain one by one, that whoever of them gains #iall give me b, and if I win, I mall do fo to them ; with every one of the reft of the Gamefters, whofe Number is/> i, I make this bargain, that whoever of them gains, HAZARDS of Game. 7 gains, (hall give me a, and I {hall give every one of them as much, if I gain : It's evident this is fair play ; for no Man here is injur'd j and in this cafe I have q Expectations to gain b y and p i Ex- pectations to gain #, and i Expectation (viz. when I win myfelf ) to get px -+- qx bq a p -f- a ; for then I am to deliver b to every one of the q Players, and a to every one of the p i Gameflers, which makes qb-\-pa a ; if therefore qx -f- bx bq ap -+- a were equal to a, I would have/> Expectations of a (fince juft now I had p i Expectations of it) and ^Expecta- tions of b, and fo would have juft come to my nrft Expectation ; therefore putting px-\-qx bq ap-\-a = a, then is x = ap -4- bq f +1 In Numbers : If I had 3 Chances to gain for 13, and 2 for 8, by this Rule, my ha- zard is worth ii; for 1 3 multiplied by 3 gives 39, and 8 by 2 1 6, thefe two added, make 55, divided by 5 is iij and I can eafily ihew, if I have n, I can come to the like Expectation again ; for playing with four others, and every one of us flaking u, with two of them I make this bargain, that whoever gains fhall give me 8, and I fhall too do fo to them ; with the other two I make this bargain, that who- ever 8 Solution of the ever gains mall give me 13, and I them as much if I gain : it appears, by this means I have two Expectations to get 8, viz. if any of the firft two gain, and 3 Expec- tations to get 13, viz. if either I or any of the other two gain ; for in this cafe I gain the Stakes, which are 55, out of which I am oblig'd to give the firft two 8, and the other two 13, and fo there re- mains 13 for myfelf. PROP. IV. fflat I may come to the Queftion proposed, viz. 'The making a juft Diftribution a- mongft Gamefters, 'when their Hazards are unequal } ive muft begin with the moft eafy Cafes. SUppofe then I play with another, on condition that he who wins the three firit Games mall have the Stakes, and that I have already gain'd two, I would know, if we agree to break off the Game, and part the Stakes juftly, how much falls to my mare ? The firft thing we muft confider in fuch Queftions is the number of Games that are wanting to both : For Example, if it had been agreed betwixt us, that he mould have the Stakes who gain'd the firft 20 Games, HAZARDS of Game. Cy Games, and if I had gain'd already 19, and rny Fellow-Gamefler but 18, my ha- zard is as much better than his in that cafe, as in this propofed, viz. When of 3 Games I have 2, and he but one, becaufe in both cafes there's 2 wanting to him, and i to me. In the next place, to find the portion of the Stakes due to each of us, we muft confider what would happen if the Game went on j it is certain, if I gain the firft Game, I get the Stake, which I call a , but if he gain'd, both our Lots would be equal, and fo there would fall to each of us ~a -, but iince I have an equal hazard to gain or lofe the firfl Game, I have an equal Expectation to gain a, or a, which, by the firft Propofition y is as much worth as the half Sum of both, /. e. %a, fo there is left to my Fellow-Gamefter a ; from whence it follows, that he who would buy my Game, ought to pay me for it %a > and therefore, he who undertakes to gain one Game before another gains two, may wager 3 to I ' PROP; liO Solution of the PHOP. V. Suppofe Iivant but one Game, and my Fellow-* Gamefier three, it is required to make a juji ibijlribution of the Stake. LE T us here likewife confider in what ftate we mould be, if I or he gain'd the firft Game j if I gain, I have the Stake a, if he, then he wants yet 2 Games, and I but i, and therefore we mould be in the fame Condition which is fuppofed in the former Proportion j and fo there would fall to my Share, as was demonftrated there, ^a ; therefore with equal facility there may happen to me a, or A^ which, by the firft Proportion, is worth ^, and to my Fel- low-Gamefter there is left -#, and there- fore my hazard to his is as 7 to i. As the Calculation of the former Propo- fition was requifite for this, fo this will ferve for the following. If I mould fup- pofe myfelf to want but one Game, and my Fellow four, (by the fame Method) you will find -j-f of the Stake belongs to- me, and -^ to him. PROP. HAZARDS of Game. \ t PROP. VI. Suppofe I want two Games, and my Fellow* Gamejler three. THEN by the next Game it will hap- pen that I want but one, and he three, which (by the preceding Proportion) is worth ^a j or that we mould both want two, whence there will be \a due to each of us : now I being in an equal probability to gain or lofe the next Game, I have an equal hazard to 'gain ^a or \a, which by the firft Proportion is worth ^a j and fo there are eleven parts of the Stakes due to me, and five to my Fellow. PROP. VII. Let us fuppoje I want two Games, and my Fellow four. IF I gain the next Game, then I mall want but one, and my Fellow four -, but if I lofe it, then I {hall want two, and he three : So I have an equal hazard for gaining ^-f a t or 4.^7, which, by the firfr, is worth -iftf : So it. appears, that he who is to gain two Games ior the other's four, i in a better condition than he who is to. C 2 t % Solution of tie gain one for the other's two ; for my {hare in the firfl cafe is ^a or LLa y which is lefs than ~L ) my mare in the laft. PROP. VIII. Let us fuppofe three Gamefters, whereof the Jirji and fecond 'want i Game, but the third 2. TO find the mare of the fir ft, we muft confider what would happen if ei- ther he, or any of the other two gain'd the firft Game j if he gains, then he has the Stake a ; if the fecond gain, he has nothing; but if the third gain, then each of them would want a Game, and fo La would be due to every one of them. Thus the firft Gamefter has one Expectation to gain a y one to gain nothing, and one for La, (fince all are in equal probability to gain the firft Game) which by the fecond Propofition is worth a : Now fince the fecond Gamefter's Condition is as good, his Share is like wife %a, and fo there remains to the third ^a, whofe Share might have been as eafily found by itfelf. HAZARDS of Game, 13 PROP. IX. In any number of Gamefters you pleafe, a- mongft whom there are fome who want, more, fome fewer Games : To find what is any one's Jhare in the Stake, we muft conjider what would be due to him, whofe Share we inveftigate, if either he, or any of his Fellow-GameJiers fiould gam the next following Game j add all their Shares together, and divide the Sum by the num- ber of the Gamejlers, the Quotient is his Share you were feeking. SUppofe three Gamefters A, B, and C ; A wants i Game, B 2, and Clikewife 2, I would find what is the fliare of the Stake due to B, which I {hall call q. Firft, we muft confider what would fall to B's Share, if either he, A, or C, wins the next Game ; if A wins, the Game is ended, fo he gets nothing ; if B himfelf gain, then he wants i Game, A i, and C 2 ; therefore, by the former Proportion, there is due to him in that cafe %q, then if C gains the next play, then A and C would want but i, and -B 2; and there- rfore, by the eighth Propofition, his Share would be worth ^q ; add together what is due to B in all thefe three Cafes, viz. o|f , 14- Solution of the ^.q, the Sum is |^, which being divided by 3, the number of Gamefters, gives ^q, which is the Share of B fought for : The Demonftration of this is clear from the fecond Propofition, becaufe B has an equal hazard to gain c$q or L^ that is "*rfo"H y > i. e. -f\q : now it's evident the Divifor 3 is the number of the Gamefters. To find what is due to one in any cafe j viz. if either he, or any of his Fellow- Gamefters win the following Game ; we rnuft confider firft the more fimple Cafes, and by their help the following j for as this Cafe could not be folv'd before the Cafe of the eighth Propofition was calcu- lated, in which, the Games wanting were i, i, 2 ; fo the Cafe, where the Games wanting are i, 2, 3, cannot be calculated, without the Calculation of the Cafe, where the Games wanting are i, 2, 2, (which we have juft now perform'd) and likewife of the Cafe, where the Games wanting are i, i, 3, which can be done by the eighth: And by this means you may reckon all the Cafes comprehended in the following Tables, and an infinite number of others. Games HAZARDS of Game. Games wanting Their Shares Games wanting Shares i,l,Z\ 1,2,2, 4,4,1 ',3, 3,n.i.liQ,6,3, *7 a 7 , 40,1 1 121, 1 21,1 li 78,158,7 1 j;42, 179, 243 729 Games wanting 1,3,3} i, 3, 4 Their Shares |6 ; , 8, 81616,82,31 629,87,13 729 729 Games wanting Their Shares Games wanting Their Shares 729 729 2. 1, 3 2, 3, 4 2, 3 f '33, 55,^5 4>,i95> 8 3 433,635, 1 19 243 729 1187 As for the Dice; thefe Queftions may be propofed, at how many Throws one may wager to throw 6, or any Number below that, with one Die j How many Throws are required for 1 2 upon two Dice ; or 1 8 on 3 j and feveral other Queftions to this purpofe. For the refolving of which, it muft be confider'd, that in one Die there are fix different Throws, all equally probable to come up ; for I fuppofe the Die has the exaft 1 6 Solution of tie exact figure of a Cube : On two Dice there are 36 different throws ; for in re^ fpedt to every throw of one Die, any one throw of the 6 of the other Die may come up; and 6 times 6 make 36. In three Dice there are 216 different throws; for iii relation to any of the 36 throws of two Dice, any one of the fix of the third may come up; and 6 times 36 make 216: So in four Dice there are 6 times 216 throws, that is, 1296 : And fo forward you may reckon the throws of any num- ber of Dice, taking always, for the Addi- tion of a new Die, 6 times the number of the preceding. Befides, it mufl be obferv'd, that in two Dicfe there is only one way 2 or 12 can come up ; two ways that 3 or 1 1 can come up ; for if I fhall call the Dice A and B, to make 3 there may be i in A, and 2 in B, or 2 in A, and i in B ; fo to make 1 1, there may be 5 in A, and 6 in B, or 6 in A, and 5 in B ; for 4 there are three Chances, 3 in A, and i in B, 3 in B, and i in A, or 2 as well in A as B ; for i o there are 'Jikewife three Chances ; for 5 or 9 there are four Chances ; for 6 or 8 five Chances ; for 7 there are fix Chances. I In HAZARDS of Game. 17 ' 3 or 18 i 4 or 17 5 or 1 6 6 or 15 3 6 10 7 or 14 8 or 13 '5 21 9 or 12 2 5 . 10 or ii 2 7 In 3 Dice there are found for PROP. X. To find at how many times one may under-^ take to throw 6 with one Die. IF any mould undertake to throw 6 the firft time, it's eviden Where's one Chance gives him the Stake, and five which give him nothing; for there are 5 throws a- gainft him, and only one for him. Let the Stake be call'd a, then he has one Ex- pectation to gain #, and five to gain no- thing, which, by the third Proportion, is worth 0, and there remains for the other tf j fo he who undertakes, with one Dif, to throw 6 the firft time, ought to wager only i to 5. 2. Suppofe one undertake, at two Throws of i Die, to throw 6, his Hazard is cal- culated thus ; if he throw 6 at the firft, he has a the Stake ; if he do not, there re- mains 1 8 Solution of the mains to him one throw, which, by the former Cafe, is worth ^a ; but there is but one Chance which gives him 6 at the firft throw, and five Chances againft him; fo there is one Chance which gives him a> and five which give him .*, which by the fecond Pro^ofition, is worth J^a, fo there remains to his Fellow-Gamefter * -, fo the Value df my Expectation to his, is as n to 25, /. . lefs than i to 2. By the fame method of Calculation, you will find, that his hazard who undertakes to throw 6 at three times with one Die, is T 9 T V tf *~ tnat he can only lay 9 1 a- gainft 125, which is fomething lefs than 3 to 4. He who undertakes to do it at four times, his hazard is T VyV^ f he may wager 67 r againft 625, that is, fomething more than 1 to i. He who undertakes to do it at five times, his hazard is yff j-0, fo he can wager 4651 againft 3125, that is, fomething lefs than 3 to . 2 - His hazard who undertakes to do it at 6 times, is ^-f-r tf > an ^ ^ e can wa g er 3 IO 3 r againft 15625, that is, fomething leis than 2 to i. Thus any number of throws may be eafily found ; but the following Propoiition will fhew you a more compendious way of Cal- culation, PROP. HAZARDS of Gam& 1 9 PROP. XT. To Jlnd at hoiu many times one may undertake to thrt/iv 1 2 with two Dice. IF one fhould undertake it at one throw, it's clear he has but one Chance to get the Stake a, and 35 to get nothing ; which, by the third Proportion, is worth ~ r a. He who undertakes to do it at twice, if he throw 1 2 the firft time, gains a j if otherwife, then there remains to him one throw, which, by the former Cafe, is worth ~^a ; but there is but one Chance which gives 12 at the firft throw, and 35 Chances again ft him j fo he has i Chance for a, and 35 for Ts- a > which by the third Proportion is worth T-J-JT^J and there remains to his Fellow-Gamefter 44^. From thefe it's eafy to find the Value of his hazard, who undertakes it at four times, palling by his cafe who undertakes it at three times. If he who undertakes to do it at four times throws 12 the firfl or fecond Caft, then he has a -, if not, there remains two other throws, which, by the former Cafe, are worth T ^ T a $ but for the fame reafon, in his two firit throws, he has 7 1 Chances which give him a, againft 1225 Chances, D 2 i* 20 Solution of the in which it may happen otherwife j there- fore at firft he has 71 Chances which give him a, and 1225 which give him -r^-J-ytf, which by the third Proportion is worth, ^JLy.. 1 ^ which mews that their hazards to one another are as 178991 to 1500625. From which Cafes it is eafy to find the Value of his Expe&ation, who undertakes to do it at 8 times, and from that, his Cafe who undertakes to do it at 1 6 times ; and from his Cafe who undertakes to do it at 8 times, and his likewife who undertakes to do it at 1 6 times ; it is eafy to determine his Expectation who undertakes it at 24 times: In which Operation, becaufe that which is principally fought, is the number of throws, which makes the hazard 'equal on both fides, viz. to him jyvho under- takes, and he who offers, you may with- out any fenfible Error, from the Numbers (which elfe would grow very great) cut off fome of the laft Figures. And fo I find, that he who undertakes to throw 12 with two Dice, at 24 times, has fome lofs ; and he who undertakes it at 25 times, has fome advantage. PROP* HAZARDS of Game. 2t PROP. XII. tfojind with how many Dice one can under*, take to throw two Sixes at the firft Caft. THIS is as much, as if one would know, at how many throws of one Die, he may undertake to throw twice fix : now if any fhould undertake it, at two throws, by what we have fhewn be- fore,, his hazard would be T V*j he who would undertake to do it at 3 times, if his firft throw were not 6, then there would remain two throws, each of which muft be 6, which (as we have {aid) is worth ^a ; but if the firft throw be 6, he wants only one 6 in the two following throws, which by the tenth Propofition, is worth 0-^a : but fince he has but one Chance to get 6 the firft throw, and five to mifs it ; he has therefore, at firft, one Chance for ^a, and five Chances-for - l ^a, which, by the third Propofition, is worth T VV*> or -sr a > a ^ ter this manner ftill afluming i Chance more, you will find that you may undertake to throw two Sixes at 10 throws of one Die, or i throw of ten Dice, and that with fome advantage. PROP. Solution of the PROP. XIII. Jflam to play with another one Throw, on this condition, that if j comes up I gain, if 10 he gains ; if it happens that we muft divide the Stake, and not play, to find how much belongs to me, and how much to him. BEcaufe of the 36 different Throws of the two Dice, there are fix which give 7, and 3 which give 10, and 27 which equals the Game, in which cafe there is due to each of us \a : But if none of the 27 fhould happen, I have 6, by which I may gain a, and 3, by which I may get nothing, which by the third Proportion, is worth ^a ; fo I have 27 Chances for a, and 9 for ^a, which, by the third Propo- iition, is worth ~^a, and there remains to my Fellow-Gameiler ~^a. PROP, HAZARDS of Game. 23 PROP. XIV. If I were playing with another by turns, with two Dice, on this condition^ that if I throw 7 I gain, and if he throw 6 be gains, al- lowing him the firjl throw : To find the pro- portion of my Hazard to his. SUppofe I call the Value of my Hazard x, and the Stakes a, then his Hazard will be a x ; then whenever it's his turn to throw, my Hazard is x, but when it*s mine, the Value of my Hazard is greater. Suppofe I then call it y ; now becaufe of the 36 throws of two Dice, there are five which give my Fellow-Gamefter 6, thirty- one which bring it again to my turn to throw, I have five Chances for nothing, and thirty-one for y, which, by the third Propofition, is worth A^-y j but I fuppos'd at firft my Hazard to be x ; therefore |y s= x, and confequently y = .|4*- I fuppos'd likewife, when it was my turn to throw, the Value of my Hazard was y ; but then I have fix Chances which give me 7, and confequently the Stake, and thirty which give my Fellow the Dice, that is, make my Hazard worth x ; fo I have fix Chances for a, and thirty for x, which, 24 Solution of the which, by Propofit. 3. is worth but this by fuppofition is equal to y, which is equal (by what has been prov'd already) to-g*, therefore 2^ == **, and confequently x = ^^a y the Value of my Hazard, and that of my Fellow-Gamefter is J4#, fo that mine is to his as 3 1 to 30. Here follow feme ^uejiions which ferve to exercije the former Rules. 1. A and B play together with two Dice, A wins if he throws 6, and B if he throws 7 ; A at firft gets one throw, then B two, then A two, and fo on by turns, till one of them wins. I require the proportion of A s Hazard to B's ? Anfwer, It is as 1 03 55 to 12276. 2. Three Gamefters, A, B, and C, take 12 Counters, of which there are four white and eight black ; the Law of the Game is this, that he fhall win, who, hood-wink'd, (hall firft chufe a white Counter ; and that A fhall have the firft choice, B the fecond, and C the third, and fo, by turns, till one of them win. Quar. What is the propor- tion of their Hazards ? HAZARDS of Game. 2$ 3. ^wagers with B, that of 40 Cards, that is, 10 of every Suit, he will pick out four, fo that there (hall be one of every fuit. A's Hazard to B's in this cafe is as 1000 to 8139. 4. Suppofing, as before, 4 white Coun- ters and 8 black, A wagers with B, that out of them he (hall pick 7 Counters, of which there are. 3 white. I require the proportion of A's Hazard to J5's ? 5. A and B taking 12 Counters, each play with three Dice after this manner, that if 1 1 comes up, A (hall give one Counter to By but if 14 comes up, B mail give one to A^ and that he lhall gain who firft has all the Counters. A's Hazard to jB's is 244140625 to 282429536481. The Calculus of the preceding Problems is left out by Monf. Huygens, on purpofe that the ingenious Reader may have the fatisfa&ion of applying the former Method himfelf ; it is in moft of them more labo- rious than difficult : for Example, I have pitch'd upon the fecond and third, be- caufe the reft can be folv'd after the fame Method. 6 PROBLEM 26 Sdut'wn of tb& PROBLEM i. The firft Problem is folv'd by the Me- thod of Prop. 14. only with this difference, that after you have found the Share due to B 3 if A were to get no firft throw, you muft fubtracl from it T s r of the Stake which is due to A for his Hazard of throwing fix at the Jfirft throw. PROBLEM 2. As for the fecond Problem, it is folv'd thus 5 Suppofe jfs Hazard, when it is his own turn to chufe, be x y when it is 5's, be j, and when it is C*s, be z -, it is evident, when out of 1 2 Counters, of which there are 4 white and 8 black, he endeavours to chufe a white one, he has four Chances to get it, and eight to mifs it ; that is, he has four Chances to get the Stake a, and eight to make his hazard worthy : fox =2 ^> , and confequently y = 1 2L=^ - When it is B's turn to chufe, then he has four Chances for nothing, and eight for 'z, (that is, to bring it to C's turn) confe- quently y = ^z = l~p 4 - ; this Equa- reduc'd gives K= Q . x ~^ a . w hen it comes HAZARDS of Game. 27 comes to (7s turn to chute, then A has four Chances for nothing, and eight for x, con- fequently z=^x, therefore ^x this equation reduc'd gives x =.^a y and confequently there remains to B and C -l-Jtf, which muft be fhar'd after the fame man- ner, that is, fo that B have the firft choice, C the next, and fo on, till one of them gain $ the reafon is, becaufe it had been juft in A to have demanded T ^. of the Stake for not playing, and then the Se- niority fell to J5 > now ? a > parted be- twixt B and C', by the former Method, gives T ^ to By and T 4 T to C j fo A^ B, and C"s Hazards from the beginning were as 9* 6 > 4- I have fuppos'd here the Senfe of the Problem to- be, that when any one chus'd a Counter, he did not diminim their num- ber ; but if he mifs'd of a white one, put it in again, and left an equal hazard to him who had the following choice ; for if it be otherwife fuppos'd, A's fhare will be T y T) which is lefs than T ^.. Prob. 2. It is evident, that wagering to pick out 4 Cards out of 40, fo that there be one of every Suit, is no more than wa- gering, out of 39 Cards to take 3 which fhall be of three propofed Suits ; for it is all one which Card you draw firft, all the E a hazard 28 Solution of the hazard being, whether put of the 3 9 re- maining you take 3, of which none fhall be of the Suit you firft drew : Suppofe then you had gone right for three times, and were to draw your laft Card, it is clear that there are 27 Cards, (viz. of the Suits you have drawn before) of which, if you draw any you lofe, and 10, of which if you draw any, you have the Stake a j fo you have 10 Chances for a, and 27 for nothing, which, by Prop. 3. is worth yftf. Suppofe again you had gone right only for two Draughts, then you have 18 Cards (of the Suits you have drawn before) which make you lofe, and 20, which put you in the Cafe fuppos'd formerly, viz. where you have but one Card to draw, which, as we have already calculated, is worth JL^-a $ fo you have 18 Chances for nothing, and 20 for JL*.a, which, by Prop. 3. is worth y|-|tf. "Suppofe again you have 3 Cards to draw, then you have 9 (of the Suit you drew firft) which make you lofe, and 30 which put ycu in the cafe fuppos'd laft ; fo you have 9 Chances for nothing, and 30 for f|Jrf, which by Propof. 3. is worth -J T y_? T an ^ y ou leave to your Fellow-Gamelter |4j|- a ; fo your ha- zard is to his as 1000 to 8139. It is eafy to apply this Method to the Games that are in ufe amongft us : For Example^ HAZARDS of Game. 29 , If A and 5, playing at Backgam- mon, A had already gain'd one end of three, and B none, and if A had the Dice in his Hand for the laft throw of the fecond end, all his Men but two upon the Ace Point being already caft off: $u and leave the refl to A. Thus likewife, if you apply the former Rule to the Royal-Oak Lottery, you will find, that he who wagers that any Figure fhall come up at the firfl throw, ought to wager i againfl 31 ; that he who wagers it 30 Solution of the it fhall come up at one of two throws^, ought to wager 63 againft 961 ,- that he who wagers that a Figure (hall come up at once in three times, ought to lay 125055 againft 923521, Gfr. it being only fome- what tedious to calculate the reft. Where you will find, that the equality will not fall as fome imagine on 16 Throws, no more than the equality of wagering at how many Throws of one Die 6 mall come up, falls on three 5 the contrary of which you have feen already demonftrated : you will find by calculation, that he has the Dif- advantage, who wagers, that i of the 32 different Throws of the Royal-Oak Lottery fhall come at once of 20 times, and that he has fome advantage, who wagers on 22 times, fo the neareft to Equality is on 21 times. But it muft be remembred, that I have fuppos'd in the former Calculation, the Ball in the Royal-Oak Lottery -to be re- gular, tho' it can never be exactly fo ; for he, who has the fmalleft Skill in Geometry, knows, that there can be no regular Body of 32 fides ; and yet this can be of no Ad- vantage to him who keeps it. HAZARDS of Game. 31 To find the Value of the Throws of Dice, as to the Quantity. . : O thing is more eafy, than by the former Method to determine the Va- lue of any number of Throws of any num- ber of Dice i for in one throw of a Die^ I have an equal Chance for i, 2, 3, 4, 5, 6, confequently my Hazard is worth their Sum 21 divided by their Number 6, that is Si"- Now if one throw of a Die be worth 37, then two throws of a Die, or one throw of. two Dice is worth 7, two throws of two Dice, or one throw of four Dice is worth 14, &c. The general Rule being to multiply the Number of Dice, the Number of Throws, and 3-;- continually. This is not to be underftood as if it were an equal wager to throw 7, or above it, with two Dice at one throw ; for he who undertakes to do fo, has the Advantage by 21 againft 15. The meaning is only, if I were to have a Guinea, a Shilling, or any thing elfe, for every Point that I threw with 3 i Sol? & ion of the with two Dice at one throw, my Hazard is worth 7 of thefe, becaufe he who gave me 7- for it, would have an equal probabi- lity of gaining or loling by it, the Chances of the Throws above 7, being as many as of thefe below it : So it is more than an equal wager to throw 14 at leaft at two Throws of two Dice, becaufe it is more probable that 14 will come, than any one number befides, and as probable that it will be above it as below it -, but if one were to buy this Hazard at the rate above- mention'd, he ought juft to give 14 for it. The equal wager in one Throw of two Dice, is to throw 7 at leaft one time, and 8 at leaft another time, and fo per vices : The reafon is, becaufe in the firft Cafe I have 2 1 Chances againft 1 5, and in the fe* cond 15 Chances againft 21. HAZARDS of Game. 33 Of RAF F LING. IN Raffling, the different Throws- and their Chances are thefe ; Where it is to be obferved, that of the 216 ,, r , j-rr -T.I r i T^- Throws. Chan. different Throws of three Dice, there are only 96 that give Dou- blets, or two, at leaft, of a 3 4 6 \ 9 10 18 I J 7 3 16 6 15 4 H 9 i3 9 12 7 II 9 kind ; fo it is 4 to 5 that with three Dice you mall throw Dou- blets, and it is i to 35 that you throw a Raffle, or all three of a kind. It is evident likewife, that it is an even wager to throw 1 1 or above it, becaufe there are as many Chances for 1 1, and the Throws above it, as for the Throws below it ; but tho' it be an even wager to throw 1 1 at one Throw, it is a difad vantage to wager to throw 22 at two Throws, and far more to wager to throw 33 at three Throws ; and yet it is more than an equal Wager that you mall throw 21 at two Throws in Raffling, becaufe it is as probable that you will, as that you will not throw n, a$ leaft, the firft time, an4 F mor 34- Solution of the more than probable that you will throw 10, at leaft, the fecond time. For an inftance of the plainnefs of the preceding Method, I will mew, how by iimple Subtraction, the moft part of the former Problems may be folv'd. Suppofe A and B, playing together, each of them flakes 32 Shillings, and that A wants one Game of the number agreed on, and B wants two ; to find the {hare of the Stakes due to each of them. It's plain, if A wins the next Game, he has the whole 64 Shillings j if B wins it, then their Shares are equal ; therefore fays A to B, If you will break off the Game, give me 32, which I am fore of, whether I win or lofe the next Game ; and fince you will not venture for the other 32, let us part them equally, that is, give me 16, which, with the former 32 make 48, leaving 16 to you. Suppofe A wanted one Game, and B three; if A wins the next Game, he has the 64 Shillings; if B wins it, then they are in the condition formerly fuppos'd, in which cafe there is 48 due to A ; there- fore fays A to B, give me the 48 which I am fure of, whether I win or lofe the next Game; and fince you will not hazard for the other 16, let us part them equally, that is, give me S } which, witfc the former 48, HAZARDS of Gams. 35 make 56, leaving 8 to you ; and fo all the other Cafes may be folv'd after the fame manner. Suppofe A wagers with B, that with one Die he fhall throw 6 at one of three Throws, and that each of them ftakes 108 Guineas ; to find what is the proportion of their Hazards. Now there being in one Throw of a Die but one Chance for 6, and five Chances againft it, one Throw for 6 is worth 4. of the Stake ; therefore fays B to A y of the 216 Guineas take a fixth part for your fir ft Throw, that is, 363 for your next Throw take a fixth part of the re- maining 1 80, that is, 30 > and for your third Throw, take a fixth part of the re- maining 150, that is, 25, which in all make 91, leaving to me 125; fo his ha- zard who undertakes to throw 6 at one of three Throws, is 91 to 125. Suppofe A had undertaken to throw 6 with one Die at one Throw of four, and that the whole Stake is 1296 ; fays A to B y every Throw for 6 of one Die, is worth the fixth part of what I throw for ; there- fore for my firft Throw give me 2 16, which is the fixth part of 1296, and there re- mains 1080, I muft have the fixth part of that, viz. 1 80, for my fecond Throw ; and the fixth part of the remaining 900, which is 1 50, for my third Throw j and F 2 the 36 Solution of the the fixth part of the laft remainder 750, which is 1 2 5 for my fourth j all this addedt together makes 671, and there remains to you 625 j fo it is evident, that As Hazard, in this Cafe, is to 5's 671 to 625. Suppofe A is to win the Stakes (which we fhall fuppofe to be 36) if he throws 7 at once of twice with two Dice, and B is to have them if he does not j fays B to A y the Chances which give 7 are 6 of the 36, which is as much as i of 6 5 therefore for your fiift Throw you mall have a fixth part of the 36, which is 6 ; and for your next Throw a fixth part of the remainder 30, which is 5 5 this in all makes n ; fo you leave 25 to me j fo A's Hazard is to J5's as n to 25. It were cafy," at this rate, to calculate the moft intricate Hazards, were it not that Fractions will occur j which, if they be more than 4, may be fuppos'd equal to an Unit, without caufing any remarkable Er- ror in great Numbers. It will not be amifs, before I conclude, to give you a Rule for finding in any num- ber of Games the Value of the firft, becaufe Huygens's Method, in that cafe, is fomething tedious. Suppofe A and B had agreed, that he mould have the Stakes who did win the x firft 9 "Games, and A had already won one * of HAZARDS of Game. 37 of the 9 ; I would know what mare of .B's Money is due to A for the Advantage of* this Game. To find this, take the firft eight even Numbers 2, 4, 6, 8, 10, 12, 14, j 6, and multiply them continually , that is, the firft by the fecond, the product by the third, GV. take the firft eight odd Num- bers i, 3, 5, 7, 9, n, 13, 15, and do juft fo by them, the produc~l of the even Num- ber is the Denominator, and the produd: of the odd Number the Numerator of a Frac- tion, which exprefleth the quantity of B's Money due to A upon the winning of the firfl Game of 9 ; that is, if each ftak'd a number of Guineas, or Shillings, 6?r. ex- prefs'd by the produdt of the even Num- bers, there would belong to A, of jB's Money, the Number exprefs'd by the pro- duct of the odd Numbers. For Example, Suppofe A had gain'd one Game of 4, then by this Rule, I take the three firfl even Numbers, 2, 4, 6, and multiply them con- tinually, which make 48, and the firft three odd Numbers, i, 3, 5, and multiply them continually, which make 1 5 ; fo there belongs to A JLJ, of B's Money, that is, if each ftak'd 48, there would belong to A> befides his own, 1 5 of B's. Now by Huy- gem's Method, if A wants but three Games while B wants four, there is due to A -|4 of the Stake; by this Rule there is due to 38 Solution of the to A 4| of 's Money, which is ~| of the Stake, which, with his own j. of the Stake, makes |. or .11 of the Stake; and fo in every Caie you will find Huygens's Method, and this will give you the fame Number : A Demonstration of it you may tin a Letter of Monfieur Pajcal's to Dnfieur Fermat ; though it be otherwife exprefs'd there than here, yet the confe- quence is eafily fupply'd. To prevent the labour of Calculation, I have fubjoin'd the following Table, which is calculated for two Gameflers, as Monfieur Huygens's is fot three. If each of us flake 256 Guineas in 96 V o 3 - 6 5 4 Game 63 70 80 2 ift Games 126 140 1 60 3 \ft Games Games 182 224 200 240 224 256 5 l ft Games 248 256 6 iji Games 256 192 256 2 128 I 256 2 5 6 The HAZARDS of G$me. 3 9 The Ufe of the Table is plain ; for let our Stakes be what they will, I can find the portion due to me upon the winning the firft, or the firft two Games, Gfr. of 2, 3,4, 5, 6. For Example , If each of us had ftak'd 4 Guineas, and the number of Games to be play'd were 3, of which I had gain'd i, fay, As 256 is to 96, fo is 4 to a fourth. 256 : 96 :: 4 ; if. 'To find what is the Value of hh Hazard, who undertakes, at the firft Throw, tQ caft Doublets, in any given number of Dice. In two Dice it is plain, to avoid Dou- blets, every one of the fix different Throws of the firft, can only be combin'd with five of the fecond, becaufe one of the fix is of the fame kind, and confequently makes Doublets j for the fame reafon, the thirty Throws of two Dice, which are not Doublets, can only be combin'd with four Throws of a third Dice, and three Throws of a fourth Dicej fo generally it is this Series, 6x5x4x3x2x1x0, 6x6x6x6x6x6x6, The. 40 Solution of the The fecond Series is the Sum of the Chances, and the firfl the Number of Chances againft him who undertakes to throw Doublets, each Series to be conti- nu'd fo many terms, as are the number -of Dice. For Example, If one mould under- take to throw Doublets at the firft Throw of four Dice, his Adverfary's Hazard is *** x n = , or \ , leaving to him 6x6x6x6 1296 1 8 * 44, fo he has x 3 to 5. In feven Dice, you fee the Chances againft him are o, be- caufe then there muft neceffarily be Dou- blets. HAZARDS of Game* 41 Of W H i s T. If there be four playing at Whift, it is 15 to i that any two of them /ball not have the four Honours, which I demonftrate thus. SUppofe the four Gamefters be A, B, C, D : \iA and B had, while the Cards are a dealing, already got three Honours, and Wanted only one, lince it is as probable that C and D will have the next Honour, as A and E ; if A and B had laid a Wager to have it, there is due to them but | of the Stake : If A and B wanted two of the four, and had wager'd to have both thofe two, then they have an equal hazard to get nothing, if they mifs the firfl of thefe two, or to put themfelves in the former Cafe if they get j fo they have an equal Ha- zard to get nothing, or -J, which, by Prop. i. is worth * of the Stake ; fo if they want three Honours, you will find due to them 4- of the Stake j and if they wanted four, -rr f ^ e Stake, leaving C and D 4^; foC and> can wager 15 to i, that G A 42 Solution of the A and B mall not have all the four Ho- nours. It is n to $ that A and B Jhall not have three of the four Honours^ which I prove thus : It is an even Wager, if there were but three Honours, that A and B mall have two of thefe three, fince 'tis as probable that they will have two of the three, as that C and JD (hall have them ; confe- quently, if A and B had laid a Wager to have two of three, there is due to them 1 of the Stake. Now fuppofe A and B had wager'd to have three of four, they have an equal hazard to get the firft of the four, or mifs it ; if they get it, then they want two of the three, and confequently there is due to them ! of the Stake j if they mifs it, then they want three of the three, and confequently there is due to them f of the Stake j therefore, by Prop. i. their Hazard is worth T s r , leaving to C and D -K.. A and B playing at Whift againft G and D; A and B have eight of ten, and C and T) nine, and therefore can't reckon Honours j to find the proportion of their Hazards. There HAZARDS of Game. 43 There is T s r due to A and B upon their hazard of having three of four Honours > but fince C and D want but one Game, and A and $ two, there is due to A and j5 but -y, or T ^ more upon that account, by Prop. 4. this in all makes T 9 r , leaving to C, and D T T T j fo the hazard of A and 5 to that of C and Z), is as 9 to 7. In the former Calculations I have ab- ftra&ed from the fmail difference of having the Deal, and being Seniors. All the former Cafes can be calculated by the Theorems laid down by Monfieur Huygens $ but Cafes more compos'd re- quire other Principles : for the eafy and ready Computation of which, I mall add pjie Theorem more, demonftrated after Mon- fieur Huygens's Method. TH EORE M. If I have p Chances for a, q Chances for b t and r Chances for c, then my hazard is worth ap+ q ^ cr ; that is, a multiplied /-t-?-H r into the number of its Chances added to b, multiplied into the number of its Chan- ces, added to c, multiplied into the num- ber of its Chances, and the Sum divided by the Sum of Chances of a, b t c. G 2 To ^4 Solution of the To inveftigate as well ,as demonn;ra.te this Theorem, fuppcfe the value of my ha- zard be x, then x muft be fuch, as having it, I am able to purchafe as good a hazard again in a juft and equal Game. Suppofe the Law of it be this, That playing with fo many Gamefters as, with myfelf, make up the number pj-q-\-r t with as many of them as the number p reprefents, I make this bargain, that whoever of them wins mall give me a, and that I (hall do fo to each of them if I win j with the Game- fters reprefented by the number of q y I bargain to get ^, if any of them win, and tp give b to each of them, if I win my felf j and with the reft of the Gamefters, whofe number is r< i, I bargain to give, or to get c after the fame manner ; Now all being in an equal probability to gain, I Jiave^ Chances to get a y q Chances to get b, and r- i Chances to get r,-and one Chance, viz. when I win myfelf, to get fx -f- qx -+-rx ap bq re -h c , which, if it be ibppos'd equal to c , then I have p Chances for a, q Chances for b t and r Chances for c (for I had juft now r i Chances for it) and therefore, in cafe px -f- qx -+- rx ap bq rc-i-c = c, then is ... */. 4- fy 4- t r By HAZARDS of Game. 45 By the fame way of reafoning ou will find, If I have p Chances for f the hazard of the Carter is to that of the Setter as 1396 to 1439. It is plain, that in every cafe the Ca- rter has the Difadvantage, and that V, or IX, are better Mains to fet on than VII, becaufe, in this laft Cart, the Setter has but 1 8 and -J4> or jVo-J whereas, when V or IX is the Main, he has 183- ; likewise VI, or VIII, are better Mains than V, or IX, becaufe .J-yJ. is a greater Fraction than TTT- All thofe Problems fuppofe Chances, which are in an equal probability to hap- pen > if it fhould be fuppos'd otherwilc, there will arife variety of Cafes of a quite different HAZARDS of Game. 49 different nature, which, perhaps, 'twere not unpleafant to conlider : I ihall add one Pro- blem of that kind, leaving the Solution to thofe who think it merits their pains. In Parattelipipedo cujus laterafunt ad in- i)icem in ratione a, b, c : Invenire quota vice quivisfufcipere poteft, ut datum quodvis fla- num, v.g. nbjaciaf. A DEMONSTRATION O F T H E 4 Gain of the BANKER In any Circumftarice of the Game call'd Pharaon* And how to determine the ' Odds at the ACE of HEARTS, or FAIR CHANCE ; With the ARITHMETICAL SOLUTION of fome Queftions relating to LOTTERIES: -And a few Remarks upon HAZARD and BACKGAMMON, L S3 J Of the Game of PH A R A o N. N order to demonftrate the Odds or Gain of the Banker in any circumftance of the Game of Pharawi, it will be neceflary to folve the following Problem. P R O B. I. Two Perfons A, B, out of a heap of 9 Cards, four of which are red and five black, un- dertake to draw a red one blindfold^ ' and he fiall be reputed to win that draws the firft : Now fuppofmg A to have the firft choice,, B the jecond, A the third, and Jo on by turns till one of them wins ; Qusere, 'The proportion of their Hazards ? SOL u TION. Let n be the number of ail the Cards, r the number of red ones, b the number of black 54 Of the Game black ones, and i the whole Stake, or the Sum play'd for. i, Since A has r Chances for a red Card, and b Chances for a black one, it follows by the third Propofition that his Expe&a- tion is worth -^ b or of the Stake, e- qual to x i ; and accordingly let it be agreed between the two Gamefters, that inftead of yfs attempting to draw a red Card he mall actually take out a black one, and as an equivalent mall have -^ paid him out of the Stake, which being done, there will remain i = ^^ =- . n n n 2, Since the remaining Cards are # r, and B has r Chances for a red Card, it fol- lows that his Probability of winning will be -^ , and confequently his Expectation upon the remaining Stake will be -~ x = - Butinfleadof B'sdraw.- n n x n I ing, we will fuppofe the Sum ny j n ^ l paid him out of the Stake, and that a black Card being taken out of the heap as before, then the remaining Stake will be ^ rb bxn i b x n b bxb i X I X i """ X I """"*" x n l * 3; of PHARAON. 55 3% Now it comes to 4's turn again to chufe ; and fince he has ftill r Chances for a red Card, and the number of remaining Cards are n 2, his Probability of winning this time will be - , and his Expectation upon the remaining Stake a * a ~| will be ~* ~ ' * ~r > which we will likewife fuppofe to be paid him out of the Stake, and then there will remain ""?. --. n-n.ii l 3x3 i x r 3x3 jx 2 xg ^ , or nxn _ l x a " b X b IX b bxb ix3 2 c == - OUt Of X a I X 2 - X I X 2 7 1-1 T-. 1 3x3 1x3 2Xr which B may have IX 2X 3 and fo we may proceed till the whole Stake is exhaufted. But I hope what has been faid is fufficient to fee the Law of Continuation, and form this general Series ; viz. - -f- - P -j- + :S,r. In which 'tis evident that P, Q^, R, S, &c. denote the preceding Terms. Now to apply this Series to practice, we muft take as many Terms of it, as there are Units in b -\- i ; for fince reprefents, the number of black Cards, the number of Drawings cannot exceed b -J- 1 3 therefore take for y^the firft, 56 Of tie Game third, fifth, &c. Terms ; and for B, rfie fecond, fourth, fixth, &c . Terms, and the Sum of thole Terms will he the refpeclive Expectations of ^, B$ or becanfe the Stake is rix'd, thefe Sums will be proportional to their refpedivc Probabilities of winning. For inftance, if we apply this to the pre- fent Cafe, the general Series will be -f- 4? H- fQ^r- yR.-f- yS -f- iT. And to bring this Series into whale Numbers, let us aSurne x a whole Number, which mul- tiply'd by % ihall be a whole Number =3 P. Therefore fmce ^ = P, ^ x-J-s=Q^an4 ~ x 4 x f = R, &c. each of which Terms are to be whole Numbers: Now 'tis evi- dent that the Denominator of the Fraction reprefented by P, is an aliquot part of that reprefented by Q5 and every Denomina- tor an aliquot part of the next following, and fo the laft Denominator 9x8x7 x6x 5 x 4 is a Multiple to all the preceding De- nominators; and confequently if each Nu- merator be multiplied by it, inftead of x y and the Produces divided by their refpective Denominators, the Quotients will all be whole Numbers, this is univerfally true : But in this Cafe, if the laft Fraction 9x8x7x6x5x4 9/2. 7?6 3 * ts Denominator 126 is the leaft common, 1 0/PHARAON. 57 common Multiple to all the reft of the Fractions when reduc'd to their leaft Terms. Which being determin'd, the Terms of the Series are eafily found by the following Operation to be 56 -f- 35 -4- 20 4- 10 -4- 4-M- OPE RATION. 126 20 = R 504 60 9 ) - 6) 56=? 10 = 8 280 ~20~ 8) - 5) 4 i 140 4 7) - 4) 20 == R i =s U Wherefore aligning to ^ 56-4-20-4-4 = 80 And toB -------- 35^10+1 = 46 And their Probabilities of winning will be as 80 to 46, or as 40 to 23. And if there be never fo many Gamefters A, B, C, D, &c. the Probabilities of winning may 'as eafily be affign'd by the general Series, as for thefe two. 1 REMARK^ Of the Game REMARK. The preceding Series may in any par- ticular Cafe be eafily fhorten'd; for if r=i, then the Series will be ' If r = 2, then the Series will be - n x n I x -i -+- n 2 -+- n 3 -f- n 4, &c. If r=^, then the Series will be X .. --: X 2 x n i xw 2 -j-# 2 x 3 4-# 3 x 4 &c. If r = 4, then the Series will be 1 X n ixa 2X/; 3 -J- 2X jX/z 4. &C. Wherefore rejecting the common Multi- plica tors, the feveral Terms of thofe Series taken in due order will be proportional to the feveral Expectations of any number of Gamefters. Thus in the Cafe of this Pro- blem, where 72=9, ^ = 4, =5, the Terms of the Series will be For A. For B. 8x7x6 = 336 7x6x5 = 210 6x5x4 = ' 20 5x4x3 = 60 4x3x2 = 24 3x2x1 = 6 480 276 Hence of PHARAON. 59 Hence it follows, that the Probabilities of winning will be refpe&ively as 480 to 276, or dividing both by 12, as 40 to 23, the fame as before, The Game of PHARAON. Rules of the Play. Firft, The Banker holds a Pack of 52 Cards. Secondly, He draws the Cards one after the other, laying them alternately to his right and left-hand. Thirdly, The Ponte may, at his choice, 1 fet one or more Stakes, upon one or more Cards taken out of his parcel of 13 Cards, from the Ace to the King inclufive, call'd a Book* either before the Banker has begun to draw the Cards, or after he has drawn any number of Couples, which are com- monly call'd Pulls. Fourthly, The Banker wins the Stake of the Ponte, when the Card of the Ponte comes out in an odd place on his right- hand ; but lofes as much to the Ponte when it comes out in an even place on his left-hand. Fifthly, The Banker wins half the Ponte's Stake, when in the fame pull the Card of the Ponte comes out twice. I 2 Sixthly, 60 Of the Game Sixthly, When the Card of the Ponte, being once in the Stock, happens to be the Lift, the Ponte neither wins nor lofes. Seventhly, The Card of the Ponte being but twice in the Stock, and the two laft Cards happening to be his Cards, he then lofes his whole Stake, PR OB. II. $0 find at Pharaon the Gain of the Banker > when any number of Cards remain in the Stock ; having the number of times that the Ponte 's Card is contain d in it, given. WHerefore this Problem admits of four Cafes, fince the Ponte's Card may be contain'd either once, twice, thrice, or four times in the Stock, Solution of the firfr, CASE. The Banker, according to the Law of the Game, has the following number of Chances for winning and lofmg ; viz. i Chance for winning i i Chance for loiing i i Chance for winning i i Chance for lofmg i i Chance for winning i i Chance for lofmg o Hence of PHARAON* 6* Hence the Banker has one Chance more for winning than for lofing, and the num- ber of all the Chances are equal to , the number of Cards in the Stock j therefore -1 33 the Gain of the Banker upon the Stake. To illuftrate this Cafe, Let it be required to find the Gain of the Banker, when there are 20 Cards re- maining in the Stock, and the Ponte's Card but once in it, =3 n 20 He gains the twentieth part of his Stake. Solution of the fecond CASE. By the Remark belonging to the pre- ceding Problem, it appears, that the Chances which the Banker has to win or lofe his Stake would be proportional to thefe Num- bers n i, n 2, n 3, &G. were the Banker not aliow'd half the Stake upon drawing of Doublets, or the Ponte's Card twice together ; upon which account the number of Chances reprefented for the Ban- ker by i for winning, mufl be divided into two parts 2, and i, whereof the firil is proportional to the probability which the Banker has for winning the whole Stake of the Ponte, and the fecond is proportional to the probability of winning the half of it: for fmce the Banker is not intitled to the i whole 62 Of the Game whole Stake upon the Ponte's Card coming out in an odd place, till he knows whether the next Card be the Ponte's, his Chance for winning the whole Stake can be no greater than the Ponte's ; becaufe there is the fame reafon, and eafily prov'd, that the fecond Card, and not the firft, mould be the Ponte's, as the firft Card, and not the fecond. Wherefore the Chances that the Banker and the Ponte have to win the whole Stake are equal, with refpect to the order of drawing, and confequently mould be ex- prefs'd by the fame number 3 whence arifcs this Scheme for determining the .number of Chances which the Banker has for win- ning and lofing the Stake, and the num- ber of Chances for winning the half Stake, jeprefented by_y. SCHEME. \ ~" Chances for winning \ n 2 Chances for lofing i 4 ^ J-Chances for winning^ n 4 Chances for lofing i ^-Chances for winning^ I n 6 Chances for lofing i i Chance for winning i Firft, Of PH ARAON. 63 Firft, $r^r- = Number of Chances for gaming y from the nature of the Scheme, and n x ^^ = Sum of all the Chances. Therefore -" ~~ 2 - is the probability of the . r X I J Banker's gaining^, and n ^ n __ l x7=the Banker's Gain upon y. Secondly, The Banker has but i Chance more to win the Stake than to lofe ; the reft for winning and lofmg being equal deftroy each other. Therefore - is the pro- /; l A n x 2 bability of getting it, and - ~ x i = n x VJ ff i Z - - is his Gain upon the Stake. a x n i Therefore the Banker's Gain vipon the i i 2 2 ti '2. X -, -4- 2 whole is - - ' *" -r- ' -r i MX ! j li y f To illuftrate this Cafe by an Example in Figures, Let it be required to find the Gain of the Banker when there are 2d Cards remaining in the Stock, and the Ponte's Card twice in it. fe = :-^=TVV = y T nearly. Anfaer, About the thirty-fourth part of his Stake. That 64 Of tie Game That x ^ J- is the Sum of all the 2 Chances, may be thus prov'd. 'Tis evi- dent by infpection of this Scheme, that they are equal to this Series n I, n 2, n __ o n 4, &c. And - x ^ ? K x a i i -f- 2 -h n 3, &c. is a Series- belonging to the preceding Problem, which exprefles the Sum of the Probabilities of winning, which belong to the two Game- flers, when the number of all the Cards is 72, and the number of red ones two. It therefore exprefles like wife the Sum of the Probabilities of winning which belong to the Ponte and Banker in the prefent Cafe, there being two of the Ponte's Cards in the Stock ; but the Sum of thefe Probabili- ties of winning are equal to Unity, becaufe the Numerators of thofe Fractions which exprefs their refpective Probabilities of win- ning being added together, is equal to the common Denominator, and fo equal to ah Unit, confequently x l_ , x i + 2 -f- 3, &c. is equal to an Unit ; wherefore putting /= i, n 2, n 3, &c. we mail have -^i x/= i, and therefore /= H^ I x "T"' Solution 65 Solution of the third CASE. By the preceding Problem, the number of Chances the Banker has for winning or lofing the Stake would be proportional to thefe Numbers n i x ;; 2, n 2 x # 3, &c. but that on account of the Doublets, the Banker's Chances for winning, as in the preceding Cafe, are divided into two parts : For inftance, n i x # 2 is divided imo the parts n 2 x n 3, and 2 x n 2 ; the former of which is proportional to the Chances that both Banker and Ponte have to win the whole Stake the firft pull, be- caufe there is the fame probability that the Ponte's Card mould be drawn the fecond time and mifs'd the firft, as drawn the firft time and mifs'd the fecond ; and the latter part, viz. 2 x n 2 is proportional to the Chances for both firft and fecond Cards be- ing the Ponte's the firft pull : and as 2 x/z 2 is eafieft found by fubtracling n 2 xn 3 from ;/ i x n 2 ; fo by fubtracting n 4 x n 5, the number of Chances that the Banker and Ponte each have, for winning the whole Stake the next pull from n i x n 4, there will remain 2x;z 4, the number of Chances for the third and fourth Card being the Ponte's, and fo for the reft : whence is eafily deduc'd the Method of K forming 66 Of tie Game forming' the following Scheme, which mews what Chances the Banker has for winning and lofing. SCH EME. 2 f-2x~ 3 ? CI f j Ji c 2 x n 23 ly n 2 x n 3 Ch. for lofing i 4*-4*-5lch .for win . C. 2 x n 43 n 4 x n 5 Ch. for lofing i f ; i x n C v 6 x 7 Ch. for lofing i Hence it appears, that there are no more Chances for winning the Stake than for lofing it j fo all the Banker's Advantage in this cafe is upon the half Stake, which depends upon drawing of Doublets at one of the Pulls, and all the Chances he has for that may be found thus. By the above Scheme, 2 x n 2 is the firft Term of the Series to win v, 4 is the common difference of the reft of "the Terms, and 4 the laft Term j and fo the Sum of all the Terms by the known Laws of Arith- metical Progreflion is " x n ~ 2 , which di- vided RAON. 67 vided by the Sum of all the Chances = * x " "~ '- ^-^- by the preceding Problem, gives ~~rr~ f r l ^ e probability of win- ning y ; therefore 2 x j*_ t x y is the Ban- ker's Gain, equal - x< 3 _- , fuppofing ^=4. EXAMPLE. Query, The Banker's Gain when the Stock confifts of 20 Cards, and the Ponte's Card thrice in it ? 4X i 4 x 19 ~~ fT *" ~ 7T ' Anfwer, About the twenty-fifth part of his Stake. Solution of the fourth CASE. SCHEME. {^ rCh. for win. 3 x 2 x n 3 3 c y 2 x 3 x n 4 Ch. for lofing i -67 ch f C i 3 x 4 x 5-) c^ 4 x 5 x n 6 Ch. for lofing i iy 2 x i x o Chance for lofing K^2 HeTe 68 Of the Game Here alfo the Chances for winning and lofing the Stakes are equal, fo that the Banker's Gain depends upon y y the half Stake. And the Chances to win y are 13x2x1! r 2 x i Equal to<3x4x3> = 3x<4x3 03x6x5) C 6 * 5 &c. &c. And to find the Sum of thofe Produces, viz. 2x1 -4-4x3 -4- 6x5, &c. continued to any number of Terms, whofe Factors are in Arithmetical Progreffion, we muft premife the following LEMMA. Subtract the fecond Product from the third, and the third Product from the fourth, and call the Remainers firft Diffe- rences j then fubtract thofe Differences from each other, and call the Remain er a fecond Difference. See the following Scheme. 2X1= 2 1* I2 l8 Q 6x5 = 30 8 8 x 7 = 56 Now if we call the firft Product a, the fecond b, the firft of the firft Differences /, *he fecond Difference /'; and if the num- ber 0/PHARAON. 69 ber of Products which follow the firft be called x, the Sum of all the Products will be equal to a -f- x x I - -f- ' x ^ ^ x / -f- -Y X I X 2 ; x x x a . I 2 3 Or * x 12 4- -f x ^ x 18 4- X 2 Q x x 8. Or 2 4- 5-lx 4- 5** 4- i^xxx, which mul- tiplied by 3, the common Multiplier to all the Terms, the Product 6 4- 17*4-; 15** 4- 4# 3 will be the Sum of all the Chances for winning of y, whofe component Parts, by Sir IJ'aac Newton's Method of the Inven- tion of Divifors, is readily found to be 2x -f- 2, 2x -+- 4, and 4Af 3 ^ wherefore 3 l2L is the number of Chances for winning ofy. Now A; = to the number of Terms to be added, bating i, therefore make #-f- i=/>, equal to the number of Terms, and then the Chances for winning of y are .'/"H-'xiFT fi|Jt according to the Scheme it appears, that the number of Terms to be added are equal to ^ ^ > wherefore writing ^ ^ for/, and 70 Of the Game and the Chances for winning are equal to 5 , which divided by the Sum of all the Chances, viz. *Z^m-***-3 and the Quotient n _^"~ t *_ is the proba- bility of winning y. and ib zn ~~ ; x ^ \* J n i x 3 the Gain of the Banker, or - 2 """" 5 _ 2 X - IXK - 3 fuppofing y = 4. EXAMPLE. Suppofe the Stock to confift of 20 Cards, and the Ponte's Card four times in it ; y The Banker's Gain ? \\ 2 X n IX -^3 2x19x17 "" ~~ 'BT*' TT nearly. Anfiver^ T y T of his Stake accurately, or the eighteenth part of it nearly. of PHARAON. 71 A Table of Pharaon, whereby the federal Ad- vantages of the Banker ', in whatever Cir- cumftances he may happen to be^ isfeenfuf- ficiently near by injpetfion, being calculated Jrom the foregoing Theory. I* Of Cards n the Stock. The N of times the Ponte's Card is contain 'd in the Stock. But I 2 3 4 S^ 50 4 B 46 44 _42_ 40 38 Jl 34 -11 30 # * 18" 46 44 ~94~ 90 86 82 IL 74 70 66 62 Ji 54 "6T 62 60 57 54 5 2 49 46 L 41 3 50 48 _46_ 44 Jf_ 40 JL 36 34 3 2 30 28 42 40 3 J6_ 34 ji 3 28 "26" 28 2b S^ 46 _^ 33 26 24 i 24 22 2O ~7cT " 16 ~M~ 12 IO 8 J 22 2O "T8~ "76" 14 42 _ii 34 3^ 30 28 2S 22 2O J 7 22 20 IF 16 Hi 12 10 T 26 22 ~TT 14 12 14 12 Q 1C 8 n 6 72 Of the Game But if an abfolute degree of exactnefs be required, it will be eafily obtain'd from the Rules and Examples given at the end of each Cafe. However, to make all things as plain as poffible, I mail, to illuftrate the Ufe of this Table, give an Example or two. EXAMPLE i. Let it be required to find the Gain of the Banker when there are 30 Cards remaining in the Stock, and the Ponte's Card twice in it. In the firft Column feek for the Num- ber anfwering to the number of Cards re- maining in the Stock : over-againft it, and under number 2, which is at the head of the Table, you will find 54, which mews that the Banker's Gain is the fifty-fourth part of his Stake. EXAMPLE 2. Let it be required to find the Gain of the Banker when there are but 10 Cards re- maining in the Stock, and the Ponte's Card thrice in it. Again ft 10, the number of Cards in the firft Column, and under number 3, you will find 12, which denotes that the Ban- ker's Gain in this Circumftance is the twelfth part of his Stake. COROL- of PHARAON. 73 COROLLARY i. From the Con ftruc- tion of the Table it appears, that the fewer Cards there are in the Stock, the greater is the Gain of the Banker. C o R o L . 2 . The lead Gain of the Ban- ker under the fame circumftance of Cards remaining in the Stock, is, when the Ponte's Card is but twice in it, the next greater when three times, ftill greater when but once, and the greateft of all when four times. Of 74 Of the ACE (/HEARTS ; Of the A c E of H E A RT s, or FA i R CHANCE. THIS Game is pretty much in vogue, as well as that of Pharaon ; there- fore it may not be improper here to touch a little upon the Advantage or Gain that accrues to the Banker or Taliere at this, as well as of that. The manner of playing at it is as follows ; There is a Table, on which is painted a felect number of Cards, generally 31 or 25, or between thofe Numbers, limited at the fancy of the Perfon who banks the Table ; the Player flakes upon either of fuch Cards more or lefs, at his pleafure. On the Table is fixed an Engine, called a Worm, into which is put an Ivory Ball, which runs round till it drops or falls into a Socket contiguous to one of thofe Cards; and if it happens to be the Card on which the Player has flaked, he faves his Stake, and is intided to 28 or 23 times as much more, according to the number of Cards painted on the Table, and the cuilom of the Place where dr FAIR CHANCE. 75 where the Table is kept. From which De- fcription of the Game, the following Pro- blem naturally arifes. P R O B. III. ffie number of Cards upon fuch a Table ', and the number of Stakes the Ranker pays in cafe he fafes, being given ; to find the Gain of the Banker upon any Siim depofited as a Stake. RULE. FROM the number of Chances or Cards the Table confifts of, fubtract the num- ber of Stakes more by one than the Banker pays when he lofes, and multiply the Re- mainer by the value of the Stake^ and di- vide the Product by the number of all the Chances or Cards upon the Table, and the Quotient will be the Banker's Gain upon that Stake, and of the fame Denomination with it ; confequently upon two Cards h6 will have twice that Advantage, upon three Cards thrice, Gfc . foppofing the Stakes equal. EXAM. i. Suppofe a Table confifts of 31 Cards, and that the Banker pays 28 Stakes when he lofes ; %uery> His Advantage upon a Stake of 100 / ? L 2 31 j6 Of the ACE 0/ HEARTS ; 3 1 The N of all the Chances. 29 The N of Stakes paid more by one. 2 Difference. Multiply by 100 the Stake. 31)200 (6 /. 186 20 31)280(91. 279 Anfwer> 61. . But this Rule is capable of determining the Gain of the Banker when unequal, as well as equal Stakes are fet upon two or more different Cards, it being only to be considered as fo many diftindl Operations. EXAM. 2. Suppofe A, J9, C play, and flake between them ioo/. viz. A 50, B 30, 20 j Query, The Advantage of the Banker? or FAIR CHANCE. 77 5 2% 2 Difference, 30 93 7 20 3 1) 140(4 j. 124 ,6 3 1 29 _ 20 31)58^(18*. 3 r 270 248 22 31) 2 Diff. 20 "40! I 20 Hence theC^l Banker's ^B Ms Gain upon CC J Total Gain 2 5 The fame as before ; whence it follows, that let the Money be ftak'd how you will, that is, upon as many Cards in what fhape foever you pleafe, the Banker's Gain will be after the rate of 6 /. 9 T ' T per Cent, upon all the Money ftak'd. But 78 Of tie ACE of HEARTS; But for the fake of a farther Illuftration, let us fuppofe a Perfon to ftake One Pound Sterling upon each Card, to the number of 3 1, wz. all the Cards upon the Table ; in fuch inftance, 'tis plain, he's fure of win- ning, or to receive 28 /. for one of the Cards, and fave the Stake of that Card which wins j but then 'tis alfo evident upon the whole, that he mufl be a lofer two Pounds, fincehe wins only 28, and lofes 30. Wherefore by the Rule of Proportion it Follows, that if in flaking 3 1 Pounds he lofes 2, in flaking loo Pounds he will lofe 6 /. 9 T f _, which confequently is the Banker's Gain. See the Operation. /. /. /. /. s. 31: 2 :: 100 : 6. 9T ' T 100 31)200 (67. 186 20 31)280(9*. 279 Wherefore or FAIR CHANCE. 79 Wherefore the Advantage per Cent, is fo plain, that 'tis needlefs to dwell any longer upon it : However, it may not be amifs to obferve, that 'tis an equal Wager that any one Card will win once in 2 1 times, notwith- ftanding the number of all the Chances arc 3 1 i which Event is difcover'd in this or any other Table, by this general RUL E. From the number of all the Cards upon the Table, dedudt one, and multiply the Remainer by feven tenths, and the Product is the Anfwer. So in this Cafe, 31 1 =30 Multiply by ,7 21,0 And the Product 21 is the number of Trials requifite for any one Car4 to win upon an equality of Chance. Of So Of LOTTERIES. O/*LOTTERIES. IN this place I fhall confider the Solution of feveral Problems relating to Lotteries, which may be of ufe to prevent fome mif- takes that People, not vers'd in fuch Com- putations, frequently run into. For in- ftance, in the prefent Lottery for the Year 1737, where the proportion of Blanks to the Prizes is as 9 to i, 'tis natural enough to conclude, that 9 Tickets are requifite for the chance of a Prize ; and yet from mathe- matical Principles 'tis evident, that 7 Tickets are more than fufficient for that purpofe, that is, in 7 Tickets it is more likely to have a Prize than not : for this, and all other Cafes of this nature, we {hall give the Arithmetical Solution of the following Problem. PROS. IV. To find how many Tickets mujl be taken, to make it as probable that one or more Prizes may be taken as not, RULE Of LOTTERIES. 81 RULE. Multiply the number of Blanks there are to one Prize by feven tenths, and the Product is the Anfwer. EXAMPL E. Query, The number of Tickets requifite in a Lottery, whereof the number of Blanks is to the number of Prizes as 9 to i, to make it an equal Chance for one or more Prizes. 9 7 , The Product 6,3 mows there is more than an equality of Chance in 7 Tickets, but fomething lefs than an equality in 6. EXAMPLE 2. <%uery, The number of Tickets requifite in a Lottery, whereof the number of Blanks is to the number of Prizes as 5 to i, to make it an equal Chance for one or more Prizes. 5 >7 3*5 M Anfwer -, 83 Of LOTTERIES. Anfwer, The number of Tickets requi- fite to that effect is between 3 and 4. PROS. V. 70 fold bow many 'Tickets miijl be taken, to make it as pr.ebabti that five or more Prizes will be taken as not. R U L E. Multiply 1,678 always by trip number of Blanks there are to a Prize, and the Product will be the Anfwer. EXAMPLE. How many Tickets mutt be had in a Lottery, to make it as probable that two or more Prizes will be taken as not, wheri there are 9 Blanks to a Prize ? 1,678 9 Anfaer, More than 1 5 Tickets, or rather more than 1 6, as mall be prov'd farther on, tho' one might undertake upon an equality of Chance to have one at leaf! in 7 Tickets. 7'he Numbers 0,7 and 1,678 made ufe of to folve this and the preceding Problem, is the refult of determining the Limits of % in thefe Equations, war. a -\- b x = 2^, and Of LOTTERIES. 83 and a -f- b* = 2^* -f- iaxb x \ where and b y reverfing the Series z = ^/2n -f- -f- to 1,678 nearly. Hence the Value of x in all Cafes will be between ^q and 1,6785' ; but AT converges pretty foon to the laft of thofe Limits, and fo the number 1,678, when x is not too fmall, gives the Anfwer fufficiently exacft ; as in the following Example, where the Odds of the Event's happening is greater than in the former. EXAMPLE 2. Let it be required to rind in how many Throws, one may undertake upon an equa- lity of Chance, to throw three Aces twice, with three Dice ? SOLU TION. Out of the 216 Chances upon three Dice, there is but i Chance for three Aces, and 215 againfl it ; wherefore multiplying the above Of LOTTERIES. 85 above Number 1,678 by 215, and the Pro- duct 360,77 (hows, that 360 Throws, or very near it, are requilite to produce the required effect. But when x is fmall, as in the preceding Example, it needs a correction j for inflead of 15,102 Tickets, it fhould be 16,443 : which Correction is eafily had by the Rule of double falfe Pofition. For being afTur'd that x is found fomething too little, I therefore affume it equal to 1 6, and fubftitute it in the Equation i -f- - = 2 -+- and find i i the left-hand fide thereof lefs than the right by 0,1589 -, wherefore I increafe the value of x four tenths more, viz. to 16,4, and fubftitute it in the Equation as before, and {till find the left-hand fide too little by 0,0155; then I multiply crofs-ways, and proceed in the reft of the Operation accor- ding to the nature of the Rule, and find #=16,443. However, we are not deflitute of a Me- thod whereby the true value of z, and con- fequently that of x may be found directly, by the help of an infinite Series, viz. ~ + l? + y^ 3 > &c - For P u ing the Hyperbolic Log. of i H = m t mq = r, the fhnding Quantity 1,791759 86 Of LOTTERIES. = n, and 2.mq n = s. The firft T" errri of the Series, i>/;s. lubtradled from 2, will give the value of z in this cafe, true to two places of Decimals^ viz. 1,83, whence 1,83 x 9 = 16,47 ' ls tne va ^ ue f *> or true number of Tickets very near ; for three Terms of the Series make x = 1 6,44300. And if x be fmaller ftill, but fo as not to have the number of Blanks to a Prize lefs than 4,1473 (which feldom or never hap- pens in Lotteries) more places of Decimals will turn out true ; in mort, the above Series will determine the Value of z all Cafes, when q is between 4,1473, and any other num- ber how great foever. Though, as it has been obferv'd before, when q. is any thing large, 1,678^ gives x fufficiently near ; for two Terms of this Series, in the cafe of throwing three Aces twice with three Dice, make z === 1,686, and confequently x = 1,686 x 215 = 362,49, which is not two throws more than by the former Computation. Nofe, The Solution of this Equation, viz. a -+- b = zb* -4- 2xab x ~ l -|- x x x i x a'-b* 2 will give the value of x, in the Cafe of a triple Event ; and the Solution o'f this, viz. a + b = 2$* -f- 2xab x I -f- x x ^ ^ x ^^a>lf x ^3 will Of LPTTERIE s. 87 will give the value of x in the Cafe of a quadruple Event. Here follows a Table of the Limits of x from one to fix Events in- clufive. The Value of x will always be, I < ffmgle double 1 f if] g I 37 0,693? 1,678? , quadruple i quintuple P R o B. VJ. The 'Number of Tickets a Perfon has in a Lottery being given, to find the Odds again ft him whether they a// prove Prizes. RULE. To the number of Blanks to a Prize add T, and make the Sum the Denominator of a Fraction whofe Numerator is Unity ; then multiply this Fraction continually into itfelf as often as the Perfbn has Tickets in the Lottery, bating one, and from the laft Fraction thus produc'd, if Unity be taken from its Denominator, the Remains will fhew how many to I it is, that thsy all prove Prizes. EXAMPLE, 88 O/* LOTTERIES. EXAMPLE. Suppofe I have three Tickets in the Lot- tery of this Year 1737, where there are 9 Blanks to a Prize ; how many is it to one but that they are all Prizes r 9 -4- i = 10 the Denominator. v I v I To" x To" X TTT Too"o' Answer, 999 to i. N. B. This Rule is only applicable to Lotteries, or in Schemes where there are a great number of Blanks and Prizes. PROS. VII. Having the Number of Tickets, and the Num- ber and Amount of all the Prizes undrawn (it any time given, to find the Value of a Horfefor any number of Days. RULE. Multiply the number of Prizes by the Price of an undrawn Ticker, and fubtract the Product from the Amount of all the Prizes, and multiply the Remainer by the number of Days the Horfe is hired for, and referve the Product for a Dividend ; then multiply the number of undrawn Tickets by the number of Days required to draw them in, and with the Product divide the aforefaid Dividend, and the Quotient will s be the Value of the Horfe. EXAMPLE. Of LOTTERIES. 89 EXAMPLE. Let it be required to find the Value of a. Horfe for the firft Day's drawing in the" prefent Lottery, where there are 70000 Tickets at lo/ each, number of the Prizes 7000, amounting to 22^000 /. exclufive of the two Prizes for the firft and lafl Num- bers drawn, viz. 500 and iooo/. arid let us fuppofe that the whole time of Drawing will be 40 Days. '.U The N of Prizes ^ -- ----- Price of an undrawn Ticket - - 10 70000 The N of undrawn Tickets 70000 The whole time of drawing - 4.0 d. 2600000 The Amount of all the Prizes; deduc- ting 14 per Cent, is 1943607. 194360 70000 2800000) 124360,000 ( ,044 I 1200000 20 L 5 88o 12360000 "30000 Il6oOCO r /2 3 2 4 Anfaer, i o d. |. N Thofe go Of LOTTERIES. Thofe that do not chufe to divide deci- mally, may, if they pleafe, multiply the aforefaid Dividend by 960 before they di- vide, and the Quotient will be the Anfwer in Farthings -, e . g. 124360 960 7461600 1119240 28)00000) 1 193(85600 ~42~~ ""112 4) 73 101 56. 17 Which i o A. 4- would be the real Value of the Horfe j but as it's on the firft Day's Drawing, there is a probability of its being the firft drawn, in confequence of which the Owner is intitled to a Prize of 500 /. this Expectation is worth about three Half-Pence more, 'viz. the 70,000 part of the Value of 500 /. when the 14 per Cent, is taken off, which being added to the Value before found, makes i Shilling, the mathematical Value of a Horfe for the firft Day's drawing. EXAMPLE 2. Admit that 1 2 Days before the end of the Drawing, there are left in the Wheel of Of LOTTERIES. 91 of Fortune 20544 Tickets, of which 2100 are Prizes, amounting in all to 714007. Query ', The Value of a Horfe for two Days, the Price of an undrawn Ticket at that time being worth 1 1 Pounds. The Amount of all the Prizes, deduc- ting 1 4 per Cent, is 61404 Pounds. The Number of Prizes . . 2 1 oo The Price of an undrawn Ticket 1 1 2100 2100 23100 The Number of undrawn Tickets 20544 Number of Days to draw them in i_z 246528 61404 23100 246528)76608,000 ( ,310 739584 _20_ 1 S. 6,200 264960 12 246528 l8 43 20 Anfwer> 6 s, ^d. . N 2 Note, ga Of LOTTERIES. Note, Irrthefe Calculations' 'tis fuppofed^ (as is cuftomary) that if the Horfe proves a Prize during your Jockeyfhip, that i o /. or an undrawn Ticket be rtftur'd to the perfon who let it. It is alfo very plain that this Rule will ferve to value the Chance of a Ticket du- ring the whole Lottery, aJlume the number of Days it will take in drawing what ycu pleale -, wherefore to render' the Opera uon. ea'fy, fuppofe i Day. ' Ar.d altho* I have made a deduction of \^per Cent, upon the Amount of all the Prizes in the two pre- ceding Exr.mples, and at the fame time allow the Calculation to ue Agreeable to the kules of Art and Science, as being founded on the ftricttft Demonflration j yet in the preferit Cr.f ..-, I lay, the Dedudion is not quite realbnable between Buyer and Seller, and confequently none fhould be made in finding the value of a Chance for the whole time : Foi how can irbe expected that any one will give up his right in a Ticket if it proves a Prize, and fbnd to the lofs of a Guinea extraordinary' if it proves a Blank, uiz. the Djfcount upon 7 /. i o s. at the rate of i^per Cent, without a valuable coniide- ration, which is that of taking Chances, valued according to the full Amount of the Prizes, and the Price the Tickets bore when they were firft purchas'd, viz. io/. each. Of LOTTERIES. 97 This Method of proceeding will put both Parties upon an equal footing, than which, I think nothing can be more fair and equi- table. Hence I make the Chance of a Ticket for the whole time of drawing to be worth 2 /. 4*. 6J. , which, with 2d. f for the Expectation of its being either the firft or laft drawn, makes 2/. 4*. gd. f ; but if the Chance happens to prove a Prize, io/. more, or the Price of an undrawn Ticket muft be advanc'd. -However, the Market- price determines what muft be given after all ; wherefore if a Chance mould fell for more than what this Calculation makes, it is not to be wonder 'd at, fince fome con- iideration ought to be made for the rifque that the Dealers in Tickets run in having them fold under par, and for fome con- tingent Expences they are unavoidably at, in furnifhing thofe with Chances and Tickets who are willing to be in Fortune's Way. But as in all Lotteries Succefs is preca- rious, we being kept in fufpence till the Event makes known either our good or bad Fortune, fo from luch ftate of Uncer- tainty it follows, that before the Drawing is finim'd a Ticket may be fold for more or lefs than at prefent ; I mall therefore, before I conclude this Subject, mew how its real worth may be known in any cir- 2 cum fiance 94 Of LOTTERIES. cumftance of the Lottery, by which means the value of a Chance may be very accu- rately determin'd at the fame time, e. g. Multiply the Number of Blanks remain- ing in the Lottery at any time of its draw- ing, by the Price of a Blank, which is al- ways fix'd, and to the Prbduct add the Amount of all the Prizes remaining, the laft drawn included; this Sum divided by the Number of all the Tickets, izz. Blanks and Prizes, will give the value of an undrawn Ticket, which being known, the Value of a Chance for the time, during the remaining part of the Lottery, eafily flows from the afore- mentioned Rule, I mall conclude this fmall TracT: by ma- king fome Remarks, relating to Hazard and Backgammon j the truth of all which is cafily deduc'd from the preceding tions* Of HAZARD. 95 Of HAZARD. i. TF 8 and 6 are Main and Chance, one J[ may lay 155 to 169, or u to 12, that either one or the other is thrown off in two Throws. 2. And if 5 and 7, or 9 and 7 are Main and Chance, the probability of their being thrown off in two Throws is alfo as 155 to 169, or as u to 12. 3. If 5 and 8, or 9 and 8, or 5 and 6, or 9 and 6 are Main and Chance, the pro- bability of throwing one of them off in two Throws is as 7 to 9 exactly. 4. And if 7 and 4, or 7 and 10 are Main and Chance, the probability of their being thrown off in two Throws is alfo as 7 to 9. 5. If 7 and 8, or 7 and 6 are Main and Chance, one may lay 671 to 625, or 15 to 14 that one of them is thrown off in two Throws, fo he that lays an even Wager he will throw one of them off in two Throws has the beft of the Lay. Of HAZARD. 6. But if 5 and 4, or 5 and 10, or 9 and 4, or 9 and 10 are Main and Chance, he that undertakes to throw either Main or Chance in three Throws has the worft of the Lay ; for it is as 22267 to 24389, or in fmaller Terms, as 21 to 23 exceeding near ; the Ratio of 21 to 23 differing from that of 22267 to 2 43^9 only but by the ten thoufandth part of an Unit. Note alfo, that n and 12 exprefs the Ratio of 155 to 169 the neareft poffible in fuch fmall Terms, as does 15 to 14 that of 671 to 625, and are eafily difcover'd by the Rule exhibited in my Appendix to Dr. Ketl's Euclid. 7. Suppofe IV to be a Main, and the Law of the Hazard to be this ; That if the Cafter throws either II, III, IV, XI, or XII the fii-ft Throw, he mall lofe the whole Stake, and if he throws V, VI, VII, VIII, IX, or X, either of which, as it may hap- pen, mall be deem'd a Chance againfr. IV, fo which ever comes up firft wins ; Query % The Hazard of the Cafter to that of the Setter ? Anjwer^ The Hazard of the Carter is to that of the Setter as 457 to 551, or as 5 to 6 very near ; wherefore the Gain of the Setter, each Stake being a Guinea, will be T y_. equal to i s. 1 1 d. ? exactly. 8. Of HAZARD. 97 8. And at Hazard, if the Main be y t and each ftake a Guinea, the Gain of the Setter is about 3^. 9. If the Main be 6 or 8, the Gain of the Setter is about Six-pence in a Guinea. 10. But if the Main be 5 or 9, the Gain of the Setter is about 3 d. -J- in a Guinea ; whence it follows, that 5, 7 and 9 are much upon a par to fet on, and that 6 and 8 are fomething more advantageous. 11. However, if a Perfon is determined to fet upon the firfl Main that is thrown, his Advantage, fuppoling each Stake to be a Guinea, is the T |-rr f a Guinea, which when reduc'd will be found equal to 4^. |, and half a Farthing exactly. 12. Hence the probability of a Main, to the probability of no Main ; or, to fpeak in trie gaining Phrafe, a Main or no Main, is as 2016 37 to 20 1 6 -f- 37 ; that is, as 1979 to 2053 accurately, or as 27 to 28 very near ; for if one flakes 27 Guineas, the other ought not to flake quite 2 d. -*- more than 28 Guineas, which is a fmall dif- ference from the truth in fuch large Stakes as 27 and 28 Guineas. 13. If, with two Dice, one mould under- take to throw firft the two Aces, next the two Duces, next the two Threes, next the two Fours, next the two Fives, and laflly the two Sixes, the Odds again ft him would be O g8 Of HAZARD, two thoufand, one hundred, and feventy- fix Millions, feven hundred, eighty-two thoufand, three hundred, and thirty-five to one ; and tho' this might poffibly hap- pen the firft fix throws, yet the Odds are fo immenfely great againft it, that it Would probably require whole Ages to perform it in : yet notwithstanding all this difficulty in throwing firft the two Aces, next the two Duces, &c. they may with an equa- lity of Chance be undertaken to be thrown in lefs than a quarter of an Hour, in the following manner, viz. to throw away till the two Aces come up, then till the two Duces, then till the two Threes, and fo on till the two Sixes are thrown ; but to throw them fucceffively is what, never yet, is ra- tional to fuppofe,fcas been done by any one. 14. If any one mould undertake to throw a Six or an Ace with two Dice in one throw, he ought to lay 5 to 4, whereas 'tis ufual to lay an even Wager only; in which cir cum fiance the Caller has fo much the better of the lay, as in the long run to impoverifh the beft Eftates, not to fay ruin them. Tho' at firft fight it muft appear to an Eye not vers'd in thefe Speculations, a little odd, that the Setter mould not have the beft of it, fince there are but two Sixe?, and two Aces for the Cafter, and two Fives, ,two Fours, two Threes, *and two Ducesj for Of .BACKGAMMON. 99 for the Setter. And were the Points > of both Dice all made upon a regular Solid or > Body of 1 2 equal Faces, fuch as the Dode-' caedron, the Cafter would undoubtedly have the advantage ; for then he would have two to one of the lay, in as much as he would have 8 Chances for winning, 'and but 4 foV lofing : But as there are two Dice, it mufl be confidered as the happening of two Events, independent of each other, which makes the Odds, as I faid before, jufl 5 to 4- Co^OLL AR Y. Hence it follows, that 1 at 'Backgammon if two Points are open, 'tis 5 to 4 but that a Perfon enters the firft throw ; and as this Thought naturally leads me to give a Solu- tion of the reft of the Hazards, it may per- haps be acceptable if I mew the Odds of en- tring when other Points of the Table are open, and therefore mall give the following Scheme for that purpofe. SCHEME. Points open A Perfon may lay i III' f2cf 2 3 jlj i > that one enters. 4 . jf 35J j] And ioo Of BACKGAMMON. And I don't doubt, but the Knowledge of thefe Odds may enable one to play the Game in other refpeds with great advan- tage j tho* for my part I own with regard to pra&ice, that I have but very little ikili in this, or any other Game whatfoever. FINIS. A 000 031 305 6