In: Statistics and Probability
Two players A and B play a game of dice . They roll a pair of dice alternately . The player who rolls 7 first wins . If A starts then find the probability of B winning the game ?
Total sample space = 6 * 6 = 36
Sample space for rolling a 7 = {(1,6), (2,5), (3,4), (4,3), (5,2), (6,1)}
P(rolling a 7) = 6 / 36 = 1/6
Let A represents that A rolls a 7 and A' represent A does not roll a 7.
P(B winning the game) = P(A' B) + P(A' B' A' B) + P(A' B' A' B' A' B) + ...
= [(5/6) * (1/6)] + [(5/6)3 * (1/6)] + [(5/6)5 * (1/6)] + ...
= (5/6) * (1/6) / (1 - (5/6)2)
= 5/11 or 0.4545