A definitive YES
or a definitive NO answer would each be sufficient. Only an answer of MAYBE (or "sometimes yes, sometimes no") would be insufficient.
However, "definitive NO is sufficient" is not a rule that the GMAT tests regularly. For most YES/NO questions, a statement that gives sufficient information will give a "yes" answer to the question.
Out of the DS problems in OG13 and the Quant Supplement 2nd Ed, only 1 that I can find has statements that give a definitive "no" answer:
DS #136 OG13
If @ represents one of the operations +, -, and x , is k @ (L + m) = (k @ L) + (k @ m) for all numbers k, L , and m ?
(1) k @ 1 is not equal to 1 @ k for some numbers k.
(2) @ represents subtraction.
(The actual problem used a circle, not an @ symbol, but I don't know how to recreate that here!)
We can rephrase the question as
"does the operation @ represent multiplication?" as multiplication is the only operation for which
k @ (L + m) =
(k @ L) + (k @ m)
(1) k @ 1 is not equal to 1 @ k for some numbers k.
If these two are not equal, then @ must NOT represent multiplication, because k*1 = 1*k. Therefore, the answer to the question "is @ multiplication?" is "no, definitely not." Sufficient.
(2) @ represents subtraction.
Again, the answer to the question "is @ multiplication?" is "no, definitely not." Sufficient.
The answer is
D.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
