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05 Apr 2012, 13:25
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
5%
(low)
Question Stats:
87% (00:43) correct
13%
(01:24)
wrong
based on 293
sessions
History
Date
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Not Attempted Yet
If x and y are positive, what is the value of x-y?
(1) (x^2 - y^2)/ (x + y) = 4
(2) x + y = 7
(1) (x^2 - y^2)/ (x + y) = 4
(2) x + y = 7
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:
https://gmatclub.com/forum/data-sufficiency-ds-141/
https://gmatclub.com/forum/data-sufficiency-ds-141/
05 Apr 2012, 13:41
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If x and y are positive, what is the value of x-y?
(1) (x^2 - y^2)/ (x + y) = 4 --> \(\frac{(x- y)(x+y)}{x + y}= 4\) --> reduce by \(x+y\): \(x-y=4\). Sufficient.
(2) x + y = 7. Clearly insufficient.
Answer: A.
(1) (x^2 - y^2)/ (x + y) = 4 --> \(\frac{(x- y)(x+y)}{x + y}= 4\) --> reduce by \(x+y\): \(x-y=4\). Sufficient.
(2) x + y = 7. Clearly insufficient.
Answer: A.
30 Apr 2012, 11:22
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eybrj2
Ans Exp:
so we are required to find the difference between x and y
Statement 1: (x^2 - y^2)/ (x + y) = 4
by observing keenly we can get that the numerator i.e (x^2 - y^2) is in (a^2)-(b^2) so this can be written as
(a +b)(a-b) so
(x^2 - y^2)/ (x + y) = 4 => (x+y)(x-y)/(x+y)=4 =>by cancelling x+y in both numerator and denominator we are left with x-y=4 which is required ,so statement 1 is sufficient to answer the question .
Statement 2: x+y=7 as the question wanted us to solve for x-y we do nothing with x+y so statement 2 is insufficient
Answer = A.
