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Qustion from Manhattan GMAT inequalities book

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harshpamnani
 Post subject: Qustion from Manhattan GMAT inequalities book
 Post Posted: Mon Jun 20, 2011 12:39 pm 
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Students


Posts: 1
Question : Data Suficiency : What is X
1) X = 4Y-4 (2) XY =8

By solving these 2 equations, I am getting 2 values of X = -8,4
But the answer is E i.e. both equations are not sufficient.

Please guide.

This is Ques 15, Page 49, Book : Inequalities
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varun_783
 Post subject: Re: Qustion from Manhattan GMAT inequalities book
 Post Posted: Mon Jun 20, 2011 1:31 pm 
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Course Students


Posts: 263
Hi,

With data sufficiency questions, you need to have one value only. If you are getting more than one value after taking the two statements together, then it is considered insufficient.

This is slightly different from what you may have learnt in school where equations that give values are considered solvable. But data sufficiency, you need to be able to answer the question without ambiguity. Two values of x does not answer the question "What is x?" in data sufficiency.

Regards

Sunil
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jnelson0612
 Post subject: Re: Qustion from Manhattan GMAT inequalities book
 Post Posted: Thu Jun 23, 2011 8:04 pm 
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ManhattanGMAT Staff


Posts: 1857
Great explanation, Sunil.

BTW, going forward these types of questions should be posted in our forum for the Math Strategy Guides: manhattan-gmat-math-strategy-guides-f7.html

_________________
Jamie Nelson
ManhattanGMAT Instructor
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