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inequality question

This topic has 1 expert reply and 3 member replies

inequality question

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Hi,

wasn't able to solve this.

Is x > 5 ?
(1) x^2 > 25
(2) 2x + 7 > 0

the OA is C

Thanks

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(1) gives us x > 5 or x < -5. So NOT sufficient.
(2) gives us 2x > -7 . x can can be 0, -3, -2,-1, 1, 2, 3..(all positive nos)...and still the equation holds. So not sufficient.

Combining the two, we can see that the only values that satisfy both are numbers > 5. Hence x > 5. So this is sufficient.



Last edited by asamaverick on Fri Jun 18, 2010 5:44 am; edited 1 time in total

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krishna kumar wrote:
Hi,

wasn't able to solve this.

Is x > 5 ?
(1) x^2 > 25
(2) 2x + 7 > 0

the OA is C

Thanks
from 1) x^2>25
we can conclude x >+5 and x>-5 (would like to stress that x>-5 i.e x can be -4 ,-3 -2 in that case so x can be less than 5 also)


from 2 )
2x+7 >0

x>-3.5
so x will breater -3.5

so combining this we are sure x>5

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Both above answers are correct but you may be having trouble combining the answers - if x>5 or x,-5 AND x>3.5 - all three things have to be true together. Try drawing it out on a numberline with two lines representing the first statement on top and one line representing the second statement on the bottom.- the only answers that work are the answers that overlap - so the only answers that work are when x>5. Hope that helps a little bit.

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krishna kumar wrote:
Hi,

wasn't able to solve this.

Is x > 5 ?
(1) x^2 > 25
(2) 2x + 7 > 0

the OA is C

Thanks
1) x can be +-5 .thant's why we can't say for sure which argument is our x . insufficient
2)2x+7>0
2x>7
x>3.5
this also don't tell us that x>5 or not. because x can be both 4 and 6 . insufficient

1) and 2) togather is sufficient . because with 1) we know that x is 5 or -5 . from 2) we know that x is more that 3.5.

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