Aidan rolls a pair of fair, six sided dice. Let$ n$ be the probability that the product of the two numbers at the top is prime. Given that $n$ can be written as $a/b$ , where $a$ and $b$ are relatively prime positive integers, find $a +b$.

[i]Proposed by Aidan Duncan[/i]
1. To determine the probability that the product of the two numbers on the top of the dice is prime, we first need to understand the conditions under which the product of two numbers is prime. A product of two numbers is prime if and only if one of the numbers is 1 and the other number is a prime number. This is because a prime number has exactly two distinct positive divisors: 1 and itself.

2. The prime numbers less than or equal to 6 (the numbers on a six-sided die) are 2, 3, and 5. Therefore, the possible prime numbers that can appear on the dice are 2, 3, and 5.

3. For each prime number, there are two possible scenarios: the prime number can appear on the first die and 1 on the second die, or the prime number can appear on the second die and 1 on the first die. This gives us a total of 2 choices for each prime number.

4. Since there are 3 prime numbers (2, 3, and 5), and each prime number can appear in 2 different ways (as described in step 3), the total number of favorable outcomes is:
   \[
   2 \times 3 = 6
   \]

5. The total number of possible outcomes when rolling two six-sided dice is:
   \[
   6 \times 6 = 36
   \]

6. Therefore, the probability \( n \) that the product of the two numbers is prime is:
   \[
   n = \frac{\text{Number of favorable outcomes}}{\text{Total number of possible outcomes}} = \frac{6}{36} = \frac{1}{6}
   \]

7. Given that \( n \) can be written as \( \frac{a}{b} \), where \( a \) and \( b \) are relatively prime positive integers, we have \( a = 1 \) and \( b = 6 \).

8. The problem asks for \( a + b \):
   \[
   a + b = 1 + 6 = 7
   \]

The final answer is \( \boxed{7} \)