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14 Jul 2019, 07:03
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D
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Difficulty:
45%
(medium)
Question Stats:
57% (01:31) correct
43%
(01:33)
wrong
based on 159
sessions
History
Date
Time
Result
Not Attempted Yet
If ab^2 = 50, what is the value of a(a – b)(a + b)?
(1) a^3 = 8
(2) ab = –10
(1) a^3 = 8
(2) ab = –10
Pure algebraic questions like this one are no longer part of the GMAT Data Sufficiency syllabus.
For relevant Data Sufficiency questions, please check the Data Sufficiency forum:
Data Sufficiency Forum
Data Sufficiency Forum
14 Jul 2019, 07:39
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(a)(a-b)(a+b) = (a)(a^2 - b^2) = a^3 - ab^2, and since we know ab^2 = 50, the question is just asking for the value of a^3 - 50. So Statement 1 is immediately sufficient.
Using Statement 2, we have two equations:
ab^2 = 50
ab = -10
and dividing the first equation by the second (or by using substitution) we find b = -5, and we can plug that in to ab = -10 to find that a = 2 and answer the question. So the answer is D.
Using Statement 2, we have two equations:
ab^2 = 50
ab = -10
and dividing the first equation by the second (or by using substitution) we find b = -5, and we can plug that in to ab = -10 to find that a = 2 and answer the question. So the answer is D.
