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# If x is a positive integer, is (x+y) even?

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Intern
Joined: 18 Jun 2012
Posts: 21
GMAT Date: 09-17-2012
If x is a positive integer, is (x+y) even?  [#permalink]

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Updated on: 20 Nov 2016, 08:07
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45% (medium)

Question Stats:

62% (01:25) correct 38% (01:35) wrong based on 216 sessions

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If x is a positive integer, is (x+y) even?

(1) K^x*K^y =1
(2) K is not equal to 1

Originally posted by ananthpatri on 05 Aug 2012, 23:02.
Last edited by stonecold on 20 Nov 2016, 08:07, edited 2 times in total.
Edited the question.
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Re: If x is a positive integer, is (x+y) even?  [#permalink]

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06 Aug 2012, 00:54
ananthpatri wrote:
If x is a positive integer, is (x+y) even?

(1) K^x*K^y =1
(2) K is not equal to 1

(1) States $$K^{x+y}=1$$. If $$K = 1, x + y$$ can be odd or even. Not sufficient.

(2) Nothing about $$x + y$$. Not sufficient.

(1) and (2) together: Sufficient, because necessarily $$x + y = 0$$.

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Re: If x is a positive integer, is (x+y) even?  [#permalink]

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06 Aug 2012, 01:03
2
EvaJager wrote:
ananthpatri wrote:
If x is a positive integer, is (x+y) even?

(1) K^x*K^y =1
(2) K is not equal to 1

(1) States $$K^{x+y}=1$$. If $$K = 1, x + y$$ can be odd or even. Not sufficient.

(2) Nothing about $$x + y$$. Not sufficient.

(1) and (2) together: Sufficient, because necessarily $$x + y = 0$$.

x+y is not necessarily zero. If k=-1, then x+y can be ANY even number.
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Re: If x is a positive integer, is (x+y) even?  [#permalink]

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06 Aug 2012, 01:08
1
Bunuel wrote:
EvaJager wrote:
ananthpatri wrote:
If x is a positive integer, is (x+y) even?

(1) K^x*K^y =1
(2) K is not equal to 1

(1) States $$K^{x+y}=1$$. If $$K = 1, x + y$$ can be odd or even. Not sufficient.

(2) Nothing about $$x + y$$. Not sufficient.

(1) and (2) together: Sufficient, because necessarily $$x + y = 0$$.

x+y is not necessarily zero. If k=-1, then x+y can be ANY even number.

You are absolutely right. Nothing stated about K! At least the answer is still C.
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Re: If x is a positive integer, is (x+y) even?  [#permalink]

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06 Aug 2012, 01:09
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Re: If x is a positive integer, is (x+y) even?  [#permalink]

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29 Oct 2016, 11:00
ananthpatri wrote:
If x is a positive integer, is (x+y) even?

(1) K^x*K^y =1
(2) K is not equal to 1

FROM STEM , X IS +VE but x+y doesnt have to be +ve , is x+y even??

from 1

k = 1 and x+y = anything or k= -1 , x+y = even or k is anything and x+y = 0 ... insuff

from 2

k is not 1 ... insuff

both together

k can = 1 and (x+y = even ) or k = anything and (x+y = 0) .... in either case x+y is even ... suff

C
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Re: If x is a positive integer, is (x+y) even?  [#permalink]

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20 Nov 2016, 08:12
Okay
so we need to get if x+y is even or not
x=> integer
remember => y is not specified as to being an integer.
Lets ook at statements

Statement 1
k^x*k^y=> k^(x+y)=> 1
okay if k is one then x+y can be anything => even/odd/fraction etc
hence not sufficient.
Statement 2
k≠1
no clue of x and y hence not sufficient
Lets Combine the statements
Hmm
K≠1
if k=-1 => x+y must be even as (-1)^even =1 and (-1)odd = -1
if k is any other integer except 1 and -1 then x+y must be zero.
But hey, zero is an even too.
BINGO
x+y must be always either 0 or even
Hence C
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Re: If x is a positive integer, is (x+y) even?  [#permalink]

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12 Jul 2018, 04:41
ananthpatri wrote:
If x is a positive integer, is (x+y) even?

(1) K^x*K^y =1
(2) K is not equal to 1

Statement 1: K^x*K^y =1

K^(x+y) = 1, therefore

K = 1, then x+y can odd/even
K > 1, then x+y = 0, hence even
K = -1, then x+y is even
K < -1, then x+y = 0 hence even

Statement 1 is not sufficient.

Statement 2: K is not equal to 1.

No information about x or y. Statement 2 is not sufficient.

Combining, we get K = -1, > 1 or < -1, hence x+y is even

Combining is sufficient.

Thanks,
GyM
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Re: If x is a positive integer, is (x+y) even?   [#permalink] 12 Jul 2018, 04:41
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