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1) n^2-1 is an odd integer 2) 3n+4 is an even integer

According to GMAT answer it is D but I disagree and have to say it is E because n can be 0 which is not an even number while satisfying both requirement.

Any thoughts?

Hello Ekin, welcome to the Gmat Club.

First of all I must say that zero IS an even integer, though it's neither positive nor negative.

Even number (even integer) \(n\) is of the form \(n=2k\), where \(k\) is an integer, so for \(k=0\), \(n=2*0=0\).

As for the question:

(1) \(n^2-1=(n-1)(n+1)=odd\) --> both \(n-1\) and \(n+1\) must be odd to produce an odd integer when multiplied, hence \(n\) is be even. Sufficient.

(2) \(3n+4=even\) --> \(3n\) must be even --> \(n\) must even. Sufficient.

1) n^2-1 is an odd integer 2) 3n+4 is an even integer

According to GMAT answer it is D but I disagree and have to say it is E because n can be 0 which is not an even number while satisfying both requirement.

If n is an integer, is n even? (1) (n^2) - 1 is an odd integer. (2) 3n + 4 is an even integer.

I personally think it is E, because putting n as 0, both the condition are insufficient. But the OA does not include 0 as one of the conditions to check.

Please explain or am I missing something here?

Thanks, Sandeep Nerli (Taking GMAT on 30th of June, 2010)

Re: OFFICIAL GUIDE 12th Edition DS Q24 [#permalink]

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11 Jun 2010, 00:30

IMO A.

Why n=0 is not a valid condition?

sandeepnerli wrote:

If n is an integer, is n even? (1) (n^2) - 1 is an odd integer. (2) 3n + 4 is an even integer.

I personally think it is E, because putting n as 0, both the condition are insufficient. But the OA does not include 0 as one of the conditions to check.

Please explain or am I missing something here?

Thanks, Sandeep Nerli (Taking GMAT on 30th of June, 2010)

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Re: OFFICIAL GUIDE 12th Edition DS Q24 [#permalink]

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11 Jun 2010, 00:47

Sorry, I want to change my answer to D.
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Re: OFFICIAL GUIDE 12th Edition DS Q24 [#permalink]

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11 Jun 2010, 01:23

IN DS, the two given statement are correct. If you are checking for their correctness then it is wrong.

Here, both statements are true and you need to consider that for which values these 2 statements meeting the criteria.

Let me know if you have some questions.

innersanctum wrote:

if n=3( an integer) n^2-1=3^2-1=8 is not odd integer 3n+4=3*3+4=13 is not even integer.

Both these conditions are insufficient.

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Re: OFFICIAL GUIDE 12th Edition DS Q24 [#permalink]

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11 Jun 2010, 01:29

Hi,

The question clearly states that n is an integer, so n can be 0 and I agree that for n= 0 both the statements hold true, but since 0 is neither negative nor positive, I think the answer should be E, not D

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