Two fair dice are thrown. What is the probability that the sum is a prime number?

Explanation

1. 01

   There are 36 equally likely ordered pairs.

2. 02

   Prime sums 2, 3, 5, 7, 11 occur in $1 + 2 + 4 + 6 + 2 = 15$ ways: $\frac{15}{36} = \frac{5}{12}$.