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# Is product 2*x*5*y an even integer? a. 2 + x + 5 + y is an

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SVP
Joined: 04 May 2006
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Schools: CBS, Kellogg
Is product 2*x*5*y an even integer? a. 2 + x + 5 + y is an [#permalink]

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23 May 2008, 02:18
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This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Is product 2*x*5*y an even integer?

a. 2 + x + 5 + y is an even integer
b. x - y is an odd integer
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Kudos [?]: 1443 [1], given: 1

CEO
Joined: 17 Nov 2007
Posts: 3583

Kudos [?]: 4670 [0], given: 360

Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40

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23 May 2008, 02:42
I guess it is C.

1. 2*x*5*y is always even integer if x and y are integers. But for non integers, for example,x=1/3, y=1/3, the expression will not be an integer.

2. the first condition: 2 + x + 5 + y is an even integer if only x+y is an odd integer. Again, x=4/3 and y=2/3 make the result of the expression non integer value.

3. the second condition: x=4/3 and y=1/3 make the result of the expression non integer value.

4. two conditions. It is obviously that x+y and x-y can be integers only if non integers are x=a+0.5, y=b+0.5. (a and b are integers)

So, 1-st condition: x+y=a+b+1 is odd or a+b is even; 2-nd condition: a-b is odd. For any a,b It is impossible to satisfy both conditions if x or y are non integers. Therefore, C.
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Kudos [?]: 4670 [0], given: 360

Manager
Joined: 11 Apr 2008
Posts: 153

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Schools: Kellogg(A), Wharton(W), Columbia(D)

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23 May 2008, 05:33
1
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walker wrote:
I guess it is C.

1. 2*x*5*y is always even integer if x and y are integers. But for non integers, for example,x=1/3, y=1/3, the expression will not be an integer.

2. the first condition: 2 + x + 5 + y is an even integer if only x+y is an odd integer. Again, x=4/3 and y=2/3 make the result of the expression non integer value.

3. the second condition: x=4/3 and y=1/3 make the result of the expression non integer value.

4. two conditions. It is obviously that x+y and x-y can be integers only if non integers are x=a+0.5, y=b+0.5. (a and b are integers)

So, 1-st condition: x+y=a+b+1 is odd or a+b is even; 2-nd condition: a-b is odd. For any a,b It is impossible to satisfy both conditions if x or y are non integers. Therefore, C.

Good expl. I agree.

Kudos [?]: 68 [1], given: 0

Re: M16-18   [#permalink] 23 May 2008, 05:33
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# Is product 2*x*5*y an even integer? a. 2 + x + 5 + y is an

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