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# M02#32

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Senior Manager
Status: Do and Die!!
Joined: 15 Sep 2010
Posts: 326

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23 Dec 2010, 10:45
What is the value of$$x^2$$ ?

1) X= $$\sqrt{2X-1}$$

2) $$x^2$$ = $$x^3$$

why statmnt 2 isn't sufficient. we are asked to find the value of $$X^2$$. So X=0
or X=1
isn't it Yes / No question, where , when we come up with two answers we reject the solution.
Thanks
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Math Expert
Joined: 02 Sep 2009
Posts: 39662

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23 Dec 2010, 10:58
1
KUDOS
Expert's post
shrive555 wrote:
What is the value of$$x^2$$ ?

1) X= $$\sqrt{2X-1}$$

2) $$x^2$$ = $$x^3$$

why statmnt 2 isn't sufficient. we are asked to find the value of $$X^2$$. So X=0
or X=1
isn't it Yes / No question, where , when we come up with two answers we reject the solution.
Thanks

In a Yes/No Data Sufficiency question, statement is sufficient if the answer is “always yes” or “always no” while a statement is insufficient if the answer is "sometimes yes" and "sometimes no".

If the GMAT asks, in a DS question, for a value, you only have sufficient information if you can get a single numerical value for the answer.

What is the value of x^2?

(1) $$x=\sqrt{2x-1}$$ --> square both sides --> $$x^2=2x-1$$ --> $$x^2-2x+1=0$$ --> $$(x-1)^2=0$$ --> $$x=1$$ --> $$x^2=1$$, we have a single numerical value of $$x^2$$. Sufficient.

(2) $$x^2=x^3$$ --> $$x^2(x-1)=0$$ --> $$x=0$$ or $$x=1$$, we can not get a single numerical value for the answer. Not sufficient.

Hope it's clear.
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Senior Manager
Status: Do and Die!!
Joined: 15 Sep 2010
Posts: 326

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23 Dec 2010, 11:27
Only one numerical value for the answer !!! Got it...
Thanks B
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Re: M02#32   [#permalink] 23 Dec 2010, 11:27
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# M02#32

Moderator: Bunuel

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