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Source: — Data Sufficiency |
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by nervesofsteel » Wed Apr 14, 2010 3:05 am
nervesofsteel wrote:If x + y is an integer, is y an integer?
(1) x - y is an integer.
(2) x + 2y is an integer.
realized my mistake

OA B
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by eaakbari » Wed Apr 14, 2010 3:24 am
I agree the answer is B . But how did you come to the conclusion. My method of picking numbers did take time.
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by kstv » Wed Apr 14, 2010 4:41 am
nervesofsteel wrote:If x + y is an integer, is y an integer?
(1) x - y is an integer.
(2) x + 2y is an integer.
(2)x+2y = x+y+y
x+y and x+y+y are integers
possible only if y is an integer

(3) x=3/2 y = 1/2.
x+y = 2 x-y = 1
but y is not an integer.
picking fractions for x and y will be easier to disprove.
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by akhpad » Wed Apr 14, 2010 6:52 am
nervesofsteel wrote:If x + y is an integer, is y an integer?
(1) x - y is an integer.
(2) x + 2y is an integer.
Statement 1:
x + y = m, x - y = n
y = (m - n) / 2
y may or may not be integer

Insufficient

Statement 2:
x + y = m, x + 2y = n
y = n - m
y must be integer

Sufficient

Ans B
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