Problem:
In how many ways can be written as the sum of two primes?
Answer Choices:
A.
B.
C.
D.
E.
Solution:
If the sum of two numbers is odd, one number must be even and the other number must be odd. Because all primes except are odd, must be one of the summands. Because , and is not prime, there are no solutions.
Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions