Mahowny rolls two fair, six-sided dice. You don't know what the rolls were, but you are told that the sum of the two rolls is a prime. What is the probability that the sum of the two rolls is 5?
The following outcomes are prime
2, 3, 5, 7, 11
Ways to roll 2 = 1
Ways to roll 3 = 2
Ways to roll 5 = 4
Ways to roll 7 = 6
Ways to roll 11 = 2
P ( 5 given that the outcome is a prime) =
4 4
______________ = _____
1 + 2 + 4 + 6 + 2 15
