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inequality

by earth@work » Fri Feb 13, 2009 9:55 pm
If x is negative, is x < -3?
(1) x^2 > 9
(2) x^3 < -9
Ans: [spoiler]do not have correct answer with me, i guess it is D : 1)gives x<-3 & (2) gives -3<x<0 [/spoiler]
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Source: — Data Sufficiency |
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by DanaJ » Fri Feb 13, 2009 10:53 pm
1. makes for x < -3. Since x^2 > 9, this means that x is either greater than 3 or smaller than -3. But seen as how x < 0, then x < -3.
2. x^3 < -9 helps us establish that x^3 < -8, which means that x < -2. However, since x is not necessarily an integer, we cannot tell if indeed x is smaller than -3 or not. It could be -100 or -2.1.

I'd go with A on this one.
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by naaga » Sat Feb 14, 2009 7:38 am
ans should be A


stmt I is sufficient

why stmt II is not sufficient

if you take x= -3 x^3 is -27 , so sufficient which is <-9

but -3 is never < -3 , so, contradictory arises
Hence , B is insufficent
Ans must be (A)
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by earth@work » Sat Feb 14, 2009 9:26 am
thanks, i was making careless error! It is A.
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