There are 6*6 total combinations = 36 combinations.
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For A: the probability that one rolls a 9 is 4/36
(9Â = 3&6, 6&3, 4&5, 5&4)Â
For B: the probability that one rolls a 6 is 5/36Â
(6Â = 3&3, 1&5, 5&1, 2&4, 4&2)Â
So find the probability that final roll is made by A:
P(A wins)Â = P(A
wins in first roll) + P(A wins in 3rd roll) + .....Â
P(A wins)Â = 4/36 + (32/36)*(31/36)*(4/36) +
(32/36)^2 *(31/36)^2 *(4/36) + ...Â
Therefore we see that the common ratio is (32*31/36^2)Â
Sum is = (4/36) / [1 - (32*31/36^2)]Â
= 144 / 304Â
= 9 / 19Â Â Â (ANSWER)