MBA.Aspirant wrote:If c and d are positive integers and m is the greatest common factor of c and d, then m must be the GCF of c and which of the following integers?

A) c + d
B) 2+d
C) cd
D) 2d
E) d^2

A quick way here is to choose numbers and eliminate incorrect answers.

If c=4 and d=2, then m=2 (since m is the GCD of c and d)

Now check the answer choices using c=4, d=2 and m=2:

A) Is m the GCD of c and c+d? Yes. 2 is the GCD of 4 and 6 (keep it)
B) Is m the GCD of c and 2+d? NO. 2 is not the GCD of 4 and 4 (eliminate it)
C) Is m the GCD of c and cd? NO. 2 is not the GCD of 4 and 8 (eliminate it)
D) Is m the GCD of c and 2d? NO. 2 is not the GCD of 4 and 4 (eliminate it)
E) Is m the GCD of c and d^2? NO. 2 is not the GCD of 4 and 4 (eliminate it)

So, the answer must be A

Cheers,
Brent