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# m0515

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Intern
Joined: 17 Jan 2009
Posts: 2

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30 Jan 2009, 07:11
If x is a positive integer, is sqrt{x} < 2.5x - 5?

1. x < 3
2. x is a prime number

The answer I chose was E but the correct answer is A -

My rationale -

From Statement 1, we know x can only be 1 or 2, since x is a positive integer. We need to test if the answer is the same for both x . If x=1 , the answer to the question is CANNOT DETERMINE sqrt{1} = +/- 1: sqrt{1} < 2.5*1 - 5 .
For x = 2 : sqrt{2} < 0. The answer is CANNOT DETERMINE. Thus, Statement 1 is insufficient.

Statement 2 does not help much as x can be 2 or 11. The inequality does not hold consistent for both of these values. Insufficient.

Statement 1 and 2 together x = 2

Thanks

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CEO
Joined: 17 Nov 2007
Posts: 3484
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40

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30 Jan 2009, 08:57
abdemt wrote:
...the answer to the question is CANNOT DETERMINE sqrt{1} = +/- 1: sqrt{1} < 2.5*1 - 5 ....

$$\sqrt{1}=1$$ not $$\pm1$$

This was discussed in some threads that $$\sqrt{n}$$ represents a positive root and solution of equitation $$x^2=n$$ is $$\pm\sqrt{n}$$, where $$\sqrt{n}$$ is a positive number
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Intern
Joined: 17 Jan 2009
Posts: 2

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30 Jan 2009, 09:09
Thank you - that clears my doubt

Regards
SVP
Joined: 29 Aug 2007
Posts: 2420

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30 Jan 2009, 14:27
abdemt wrote:
If x is a positive integer, is $$sqrt{x}$$ < (2.5x - 5)?

1. x < 3
2. x is a prime number

The answer I chose was E but the correct answer is A - Thanks

http://gmatclub.com/forum/59-p564448?t=75172#p564448

--== Message from GMAT Club Team ==--

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If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

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Re: m0515 &nbs [#permalink] 30 Jan 2009, 14:27
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# m0515

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