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What is the cube root of w ?

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What is the cube root of w ?

by mitzwillrockgmat » Mon May 24, 2010 11:18 am
What is the cube root of w ?
(1) The 5th root of w is 64.
(2) The 15th root of w is 4.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

Another exponent related problem i am having issues with! Please help!!!! >(
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by Patrick_GMATFix » Mon May 24, 2010 11:27 am
Hey. Where is this question from plz? I only work with official questions (OGs, GMATPrep) because they make the best practice Qs for the real GMAT.
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by clock60 » Mon May 24, 2010 12:25 pm
as far as i see the query
find w^1/3-?
(1)w^1/5=64
w=(2^6)^5=2^30
so w^1/3=(2^30)^1/3=2^10-sufficient

(2)w^15=4,w=(2^2)^15=2^30
(2^30)^1/3=2^10-sufficient
so D

it is better to sent this in DS section
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by tpr-becky » Mon May 24, 2010 1:06 pm
if you need the cube root of W you are basically looking for the value of W, and then you would take the cube root.

statement 1 says the 5th root of W is 64 - becuase we know we can take 64^5 to get the value of W this answer is sufficient (don't have to actually solve it)

AD

Statement 2 is similar - it says that teh 15th root of W is 4 - again here we don't have to actually solve the problem, just know that we can - we can take 4^15 to find W and then find the cube root - becuase we know we can solve this the answer is D.

This is a good question to point out that most of the time on DS you are looking for concepts, not actual solutions.
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by mitzwillrockgmat » Tue May 25, 2010 12:15 pm
tpr-becky wrote:if you need the cube root of W you are basically looking for the value of W, and then you would take the cube root.

statement 1 says the 5th root of W is 64 - becuase we know we can take 64^5 to get the value of W this answer is sufficient (don't have to actually solve it)

AD

Statement 2 is similar - it says that teh 15th root of W is 4 - again here we don't have to actually solve the problem, just know that we can - we can take 4^15 to find W and then find the cube root - becuase we know we can solve this the answer is D.

This is a good question to point out that most of the time on DS you are looking for concepts, not actual solutions.
Thanks! often i get lost in solving ds questions, will actively try to stop the need to do so from now on...otherwise, the problem is quite easy. thanks!


@ Patrick_GMATFix - this question is part of a set of mock gmat exams from a gmat prep centre. i've been told it contains real gmat questions.
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