Is x Negative?

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nitya34: Master | Next Rank: 500 Posts; Posts: 179; Joined: Tue Jan 08, 2008 7:23 pm; Thanked: 11 times; GMAT Score:590

by nitya34 » Mon Mar 16, 2009 8:36 am

Is x a negative number?

statement 1: x^2 is a positive number
statement 2: x*lyl is not a positive number

I believe its not E its C

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Source: Beat The GMAT — Data Sufficiency | Mon Mar 16, 2009 8:36 am

Vemuri: Legendary Member; Posts: 682; Joined: Fri Jan 16, 2009 2:40 amFollowed by: 1 member; Thanked: 32 times

Re: Is x Negative?

by Vemuri » Mon Mar 16, 2009 9:12 am

My answer is B.

The question is asking if x <0. We should look for statements that give a definite YES/NO answer.

Stmt 1: The answer we get is Yes & No. Since, there is no definite answer, this statement is insufficient.

Stmt 2: x*|y| < 0. Since |y| will always yield a positive number, x has to be -ve. This statement is sufficient to answer our main question.

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nitya34: Master | Next Rank: 500 Posts; Posts: 179; Joined: Tue Jan 08, 2008 7:23 pm; Thanked: 11 times; GMAT Score:590

Re: Is x Negative?

by nitya34 » Mon Mar 16, 2009 9:33 am

What about |y|=0?

Vemuri wrote:My answer is B.

The question is asking if x <0. We should look for statements that give a definite YES/NO answer.

Stmt 1: The answer we get is Yes & No. Since, there is no definite answer, this statement is insufficient.

Stmt 2: x*|y| < 0. Since |y| will always yield a positive number, x has to be -ve. This statement is sufficient to answer our main question.

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Morgoth: Master | Next Rank: 500 Posts; Posts: 316; Joined: Mon Sep 22, 2008 12:04 amFollowed by: 1 member; Thanked: 36 times

Re: Is x Negative?

by Morgoth » Mon Mar 16, 2009 11:46 am

nitya34 wrote:Is x a negative number?

statement 1: x^2 is a positive number
statement 2: x*lyl is not a positive number

I believe its not E its C

x < 0 ?

Statement I

x^2 is a positive number

this means x is negative or positive but not 0.

insufficient.

Statement II

x*lyl is not a positive number

this means the above expression is either negative or 0

x could be negative or positive.

insufficient.

Combining I & II
x^2 is positive number
x*lyl is not a positive number

Case I

if x is negative & y is negative, x*lyl will always be negative since lyl will always be positive.

Case II

if x is positive & y = 0 x*lyl will be 0

Case III

if x is negative & y=0 x*lyl will be 0

Hence x could be negative or positive.

Insufficient.

Thus, E.

Hope this helps.

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Vemuri: Legendary Member; Posts: 682; Joined: Fri Jan 16, 2009 2:40 amFollowed by: 1 member; Thanked: 32 times

Re: Is x Negative?

by Vemuri » Mon Mar 16, 2009 6:00 pm

nitya34 wrote:What about |y|=0?
[\quote]

Ooppss....thanks for correcting

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nitya34: Master | Next Rank: 500 Posts; Posts: 179; Joined: Tue Jan 08, 2008 7:23 pm; Thanked: 11 times; GMAT Score:590

by nitya34 » Mon Mar 16, 2009 9:11 pm

thanks Morgoth

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