DS: Tough, but maybe not...

[cyber_office]

Hi,

I do not know where this question was sourced. It was sent to me by someone. I searched the Web to determine its source but was unsuccessful. Anyways, here's the problem:

What is the greatest common divisor of positive integers a and b?

(1) a and b share exactly one common factor
(2) a and b are both prime numbers

According to the problem set that was sent to me, the answer is A. I do not understand how it can be A alone.

I agree that A allows us to conclude that 1 must the GCD if it is the only shared factor and hence we can answer the question.

What I do not understand is why we can't use 2 to also positively answer the question with the answer that 1 is the the GCD. If two numbers are primes, the only number that will evenly divide them both is 1. Hence, 1 must be their GCD.

Shouldn't the answer be D?

If this question is from a banned source, please delete it. Otherwise, any reponses are greatly appreciated.

Thanks very much.

[cyber_office]

Ron/Ben/Stacey/Anyone? I greatly appreciate the help. Thanks.

[cyber_office]

Nevermind. I think I figured it out.

Statement 2 states that a and b are both prime numbers, but does not specifically state that a and b are unique prime numbers. therefore, we cannot definitely determine the GCD. Statement 2 is insufficient.

Thanks.