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If x + y is an integer, is y an integer?

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If x + y is an integer, is y an integer?  [#permalink]

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New post 18 Jul 2011, 04:10
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

56% (01:39) correct 44% (01:27) wrong based on 30 sessions

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If x + y is an integer, is y an integer?

(1) x – y is an integer.
(2) x + 2y is an integer.

OPEN DISCUSSION OF THIS QUESTION IS HERE: http://gmatclub.com/forum/if-x-y-is-an- ... 28412.html

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Re: If x + y is an integer, is y an integer?  [#permalink]

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New post 18 Jul 2011, 04:32
jamifahad wrote:
If x + y is an integer, is y an integer?
(1) x – y is an integer.
(2) x + 2y is an integer.


1)
x=1.5, y=0.5
OR
x=1, y=2
Not Sufficient.

2)
x+2y=integer
x+y+y=integer
We know x+y=integer
integer+y=integer
y must be an integer
Sufficient.

Ans: "B"
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Re: If x + y is an integer, is y an integer?  [#permalink]

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New post 18 Jul 2011, 05:36
B is sufficient....B is the answer
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Re: If x + y is an integer, is y an integer?  [#permalink]

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New post 18 Jul 2011, 06:53
X+2Y = b (where b is an integer)
X+Y = a (where a is also an integer)

subtracting the above y = b-a, and b-a has to be an integer as b and a are both integers.

B is sufficient.
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Re: If x + y is an integer, is y an integer?  [#permalink]

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New post 18 Jul 2011, 07:22
For B:

what if x = 3.7 and y = 2.3

x + y = integer
x + 2y = not integer

what if x = 3 and y = 2

x+y = integer
x=2y = integer

Shouldn't B also be insufficient?
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Re: If x + y is an integer, is y an integer?  [#permalink]

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New post 18 Jul 2011, 07:23
OOOOPPSS never mind! I figured it out haha.
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Re: If x + y is an integer, is y an integer?  [#permalink]

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New post 05 Dec 2017, 23:45
If x + y is an integer, is y an integer?

(1) x – y is an integer --> if x=y=0.5 then the answer to the question is NO but if x=y=1 then the answer to the question is YES. Not sufficient.

(2) x + 2y is an integer --> x+2y=(x+y)+y=integer. Since given that x+y=integer, then: integer+y=integer --> y=integer. Sufficient.

Answer: B.

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Re: If x + y is an integer, is y an integer? &nbs [#permalink] 05 Dec 2017, 23:45
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