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Newton-Pepys Problem
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NewtonPepysProblem

Samuel Pepys wrote Isaac Newton a long letter asking him to determine the probabilities for a set of dice rolls related to a wager he planned to make. Pepys asked which was more likely,

1. At least one six when six dice are rolled,

2. At least two sixes when 12 dice are rolled, or

3. At least three sixes when 18 dice are rolled.

Newton-PepysProblem

The probability of obtaining n or more sixes in a roll of 6n dice is given by

P_n=sum_(x=n)^(6n)(6n; x)(1/6)^x(5/6)^(6n-x)
(1)
=1-sum_(x=0)^(n-1)(6n; x)(1/6)^x(5/6)^(6n-x)
(2)
=(5^(5n))/(6^(6n))(6n; n)_2F^~_1(1,-5n;1+n;-1/5),
(3)

where _2F^~_1(a,b;c;x) is a regularized hypergeometric function. Values for n=1, 2, and 3 gives

P_1=(31031)/(46656) approx 0.6651
(4)
P_2=(1346704211)/(2176782336) approx 0.6187
(5)
P_3=(15166600495229)/(25389989167104) approx 0.5973
(6)

(Sloane's A143162 and A143163). Therefore, P_1 is the most likely, with P_n asymptotically approaching 1/2 as n->infty.

SEE ALSO: de Méré's Problem

REFERENCES:

Mosteller, F. "Isaac Newton Helps Samuel Pepys." Problem 19 in Fifty Challenging Problems in Probability with Solutions. New York: Dover, pp. 19 and 33-35, 1987.

Schell, E. D. "Samuel Pepys, Isaac Newton, and Probability." Amer. Statistician 14, 27-30, Oct. 1960.

Sloane, N. J. A. Sequences A143162 and A143163 in "The On-Line Encyclopedia of Integer Sequences."




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Weisstein, Eric W. "Newton-Pepys Problem." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/Newton-PepysProblem.html

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