A 6-sided die is labeled with the first prime numbers instead of the first integers to . The die is rolled twice. What is the probability that the sum of the rolls is a prime number?

Source: NCTM Mathematics Teacher 2008

**SOLUTION
**Table method

The table shows there are outcomes in which the sum of the rolls is a prime number.

Probability = .

Alternative method

Number of possible outcomes

Number of desirable outcomes

We need only look at the sum of because we want an odd sum

Of these sums only , and are prime number. We double the count to because we could toss and or and .

Probability = .

**Answer**: