[AveburySutton]

process of elimination. as soon as peter starts, all primes are off the table. Given that, some number pairs which sum to the same number as just one other number pair where the second number pair has at least one prime are off the table. And so on and so forth. My instinct was to program the solution. Bet there are people who could do it in their heads.

[caf]

It's only the primes above 50 that are immediately eliminated by the fact that Peter does not know the answer right away.

The primes below that can be present in products that have multiple possible answers: eg. we can't eliminate 47 right off the bat because Peter could have been told a product like 3290.

[corndoge]

>as soon as peter starts, all primes are off the table

How do you figure? If Peter is given 97 (a prime), how is he supposed to know that a) he's been given a product (puzzle doesn't say he was told it's a product) and b) if he knows he's been given a product how is he supposed to know 97 is prime? He wasn't told that in the puzzle either.