gmatmachoman wrote:If r - s = 3p , is p an integer?
(1) r is divisible by 735
(2) r + s is divisible by 3
Simplifying the question:
Is (r - s)/3 an integer?
or
Is (r - s) a multiple of 3?
(1) no info about s... insufficient.
(2) if r=4 and s=2, then r-s = 2. Is 2 a multiple of 3? NO
if r=6 and s=3, then r-s = 3. Is 3 a multiple of 3? YES
Can get YES and NO... insufficient.
Combined:
From (1), we know that r is a multiple of 3 (since 735 is a multiple of 3).
So, from (2), we now know that:
(multiple of 3) + s = (multiple of 3)
s = (multiple of 3) - (multiple of 3)
s = (multiple of 3)
Plugging back into our question:
Is (multiple of 3) - (multiple of 3) a multiple of 3? Definitely YES... together sufficient, choose C!
