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Is (x-y)*(x+y) an even integer? (1) x and y are integers (2)

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Is (x-y)*(x+y) an even integer? (1) x and y are integers (2)  [#permalink]

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New post 20 Nov 2008, 08:31
2
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

51% (00:45) correct 49% (01:02) wrong based on 34 sessions

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Is (x-y)*(x+y) an even integer?

(1) x and y are integers
(2) (x+y) is even
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Re: Is (x-y)*(x+y) an even integer? (1) x and y are integers (2)  [#permalink]

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New post 07 May 2010, 10:18
I marked B.
If x+y is even then whatever the value of x and y, the stated exp in question will be even.

Can someone explain why C is correct?

ritula wrote:
Is (x-y)*(x+y) an even integer?

(1) x and y are integers
(2) (x+y)is even

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Re: Is (x-y)*(x+y) an even integer? (1) x and y are integers (2)  [#permalink]

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New post 07 May 2010, 10:41
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ykaiim wrote:
I marked B.
If x+y is even then whatever the value of x and y, the stated exp in question will be even.

Can someone explain why C is correct?

ritula wrote:
Is (x-y)*(x+y) an even integer?

(1) x and y are integers
(2) (x+y) is even


Answer is C because if x and y are not integers (second statement does not state that), then x+y may be even (statement 2) and (x-y)*(x+y) may not be an integer at all.

Example:
x=1.8 and y=0.2 - answer to the question NO.
x=1.5 and y=0.5 - answer to the question YES.

Statement (1) says that x and y are integers so combined statements guarantee (x-y)*(x+y) being even.

Hope it helps.
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Re: Is (x-y)*(x+y) an even integer? (1) x and y are integers (2)  [#permalink]

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New post 07 May 2010, 23:27
yes agreed it should be C because x and y can be fractions
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Re: Is (x-y)*(x+y) an even integer? (1) x and y are integers (2)  [#permalink]

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New post 16 Sep 2017, 02:44
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Re: Is (x-y)*(x+y) an even integer? (1) x and y are integers (2) &nbs [#permalink] 16 Sep 2017, 02:44
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