Hi All,
We're told that R and S are INTEGERS. We're asked if R is divisible by 7. This is a YES/NO question and can be solved by TESTing VALUES (along with some knowledge of division).
1) The product (R)(S) is divisible by 7.
IF...
R=7 and S=1, then (R)(S) = 7 and the answer to the question is YES.
R=1 and S=7, then (R)(S) = 7 and the answer to the question is NO.
Fact 1 is INSUFFICIENT
2) S is not divisible by 7.
IF...
R=7 and S=1, then and the answer to the question is YES.
R=1 and S=1, then and the answer to the question is NO.
Fact 2 is INSUFFICIENT
Combined, we know...
The product (R)(S) is divisible by 7.
S is not divisible by 7.
Since R and S are both INTEGERS, for (R)(S) to be divisible by 7, at least one of the two variables MUST be divisible by 7. Since S is NOT divisible by 7, then R MUST be divisible by 7 - and the answer to the quesiton is ALWAYS YES.
Combined, SUFFICIENT
Final Answer: C
GMAT assassins aren't born, they're made,
Rich
