Geva@MasterGMAT wrote:I think the question is problematic - either the question is transcribed wrongly, or Manhattan didn't think this through.
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the problem with a phrasing of "is there a number" is that such a number either exists or doesn't exist - you can't create a statement that will allow the number to both exist and not exist. The answer to this question will be D, always - either the statement shows that there is such a number ("yes"), or the statement shows that there is no such number ("no"). Since a DS question should not be answerable without even looking at the statements, I believe the question itself is wrong.
There are certainly many problems with the wording of the question (if a question is going to talk about multiples, it needs to make clear the quantities concerned are integers, the GMAT never tests multiples or divisibility using negative numbers, and the question should probably make more clear that repetition of elements is not allowed), but the question doesn't suffer from the logical problem you describe. I can design a question with a similar stem to illustrate:
Z is an infinite sequence of distinct positive real numbers. Is there a number in sequence Z that is greater than every other number in Z?
1) No number in sequence Z is greater than 1.
2) 1 is in sequence Z.
Statement 1 here is not sufficient. Our sequence might be defined, for all positive integers n, by:
a_n = 1/n
in which case the sequence would be 1, 1/2, 1/3, 1/4, 1/5... In this sequence there is indeed a number, 1, which is greater than every other number. On the other hand, our sequence might be defined, for all positive integers n, by:
a_n = n/(n+1)
in which case the sequence would be 1/2, 2/3, 3/4, 4/5, 5/6, ... In this sequence, every number is greater than the number before it, and no number is ever greater than 1, but there is no number in this sequence which is greater than every other number (and that's what the question asks: is there a number which is actually in the sequence which is larger than any other number in the sequence); it just keeps getting closer and closer to 1 the further you go.
Statement 2 alone is clearly insufficient (our sequence could again be the first example I gave above, or it could be 1, 2, 3, 4, 5, ... in which case there is no number larger than every other). Combined, certainly 1 needs to be the largest element in the sequence, and the answer is C.
