crackgmat007 wrote:If positive integer x is a multiple of 6 and positive integer y is a multiple of 14, is xy a multiple of
105?
(1) x is a multiple of 9.
(2) y is a multiple of 25.

If x is a multiple of 6, then x is a multiple of 2 and 3. If y is a multiple of 14, then y is a multiple of 2 and 7. So before looking at the statements, we know that xy is a multiple of 2^2 * 3 * 7. We want to know if xy is a multiple of 105 = 3*5*7. We already know that xy is a multiple of 3*7, so we only need to know if xy is a multiple of 5 to have sufficient information. S1 doesn't tell us that, but S2 does, so S2 is sufficient.