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DS Question

by kris610 » Mon May 26, 2008 11:18 am
If x is a member of set S, then x^2 and x^3 are members of S. The only member of S that is neither a square or a cube is called the 'Source Member'. Is 8 a member of S?

A) 4 is a member of S and is not a source member.

B) 64 is a member of S and is not a source member.
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by aatech » Mon May 26, 2008 6:47 pm
I will go with A on this one

Stmt 1 - 4 is NON SOURCE member of the set, means the set is like 2, 4, 8. SUFF

Stmt 2 - 64 is a NON SOURCE member of the set.. there can be 2 cases

4,16,64 - 8 is not in this OR

8, 64, 512 - 8 is a member so NOT SUFF

OA please?
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by kris610 » Tue May 27, 2008 5:29 am
The OA is given as A. But, my question is, if 4 is a member and not a source, then -2 could be the source member, resulting in 4 being a member. In that case, -8 is a member for sure, but we don't know if 8 is. The stem doesn't say that the source member is positive or negative.
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by aatech » Tue May 27, 2008 5:46 am
When the question is talking about x^2 and x^3, I think its safe to assume x is positive...

Anyone else??
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by kris610 » Tue May 27, 2008 7:25 am
I'm not sure as the questions are pretty air-tight. What prevents me from assuming that -2 is the source member that could make both 4 and 64 members of S? 2 also results in both 4 and 64 being members of S. Any restriction on GMAT is explicit. For example, if the question involves a square root, GMAT explicitly states the number is positive and if the denominator is x-1, it would explicitly mention that x is not equal to 1.
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