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M16 Q18

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M16 Q18 [#permalink]

04 Apr 2010, 13:49

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I think the ans should be E, as y =0 and x as odd integer case is not considered.

Guys input your explanations pls.

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CEO

Status: Nothing comes easy: neither do I want.

Joined: 12 Oct 2009

Posts: 2761

Location: Malaysia

Concentration: Marketing, Entrepreneurship

Schools: Anderson '15 (D), INSEAD Jan '14

GMAT 1: 670 Q49 V31
GMAT 2: 710 Q50 V35

Followers: 124

Kudos [?]: 637 [0], given: 222

Re: M16 Q18 [#permalink]

05 Apr 2010, 14:06

Bump.... BB could u pls check this.
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Re: M16 Q18 [#permalink]

05 Apr 2010, 17:24

gurpreetsingh wrote:

I think the ans should be E, as y =0 and x as odd integer case is not considered.

Guys input your explanations pls.

In case x=odd and y=0 --> 2*x*5*y=0=even

Question: 2*x*5*y=even. As there is 2 as a multiple, then this expression will be even if 5xy=integer. Basically we are asked is 5xy=integer true?

Note that x and y may not be integers for 2*x*5*y to be even (example x=\frac{7}{9} and y=\frac{9}{7}) BUT if they are integers then 2*x*5*y is even.

(1) 2+x+5+y=even --> 7+x+y=even --> x+y=odd. Not sufficient. (x=1 and y=2 answer YES BUT x=1.3 and y=1.7 answer NO)

(2) x-y=odd. Not sufficient. (x=1 and y=2 answer YES BUT x=1.3 and y=0.3 answer NO)

(1)+(2) Sum (1) and (2) (x+y)+(x-y)=odd_1+odd_2 --> 2x=even --> x=integer --> y=integer --> Both x and y are integers. Hence sufficient.

Answer: C.
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Re: M16 Q18 [#permalink] 05 Apr 2010, 17:24

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