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overlapping ranges DS question

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Guest
 Post subject: overlapping ranges DS question
 Post Posted: Thu Mar 06, 2008 2:57 am 
Is x > 5 ?

1. x^2 > 25
2. 2x + 7 > 0

Is the answer C ?

Here is how i worked it out

1. x > 5 or x < -5
so, insufficient
2. 2x > -7
=> x > -3.5
so, insufficient

Combining the two x > 5. Hence, C.
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H_to_750
 Post subject: Yes
 Post Posted: Sat Mar 08, 2008 9:04 am 
The answer is C

In statment two we know that X is greater than - 3.5
Statment one tells is X = 5 or X = -5

When we combine we know that x is 5

So it answer the questions if X > 5 and the answer is NO it is not greater than 5 it is 5
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RonPurewal
 Post subject: Re: Yes
 Post Posted: Wed Mar 12, 2008 4:07 am 
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ManhattanGMAT Staff


Posts: 7146
H_to_750 wrote:
The answer is C

In statment two we know that X is greater than - 3.5
Statment one tells is X = 5 or X = -5

When we combine we know that x is 5

So it answer the questions if X > 5 and the answer is NO it is not greater than 5 it is 5


whoa, no.

statement (1) is an inequality. it certainly won't magically resolve itself into an equality!

as the first poster correctly observes, x^2 > 25 means that either x > 5 or x < -5. think about it conceptually: x^2 doesn't care whether x is positive or negative (because the square is always positive, no matter what). therefore, as long as the 'size' of x (regardless of sign) is at least 5, x works; hence the 2 different inequalities.

in conjunction with statement (2), the possibility that x < -5 is ruled out, so we have x > 5.
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