20q20
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Source: Beat The GMAT — Data Sufficiency |
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mals24
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IMO E
St 1: n^3(1-x^3)<0
Now we can have two situations
If n is negative then x<1
Let n=-2, x=1/3
-8(1-1/9) = -64/9
But if n is positive x is an integer.
Let n=2 x=-3
8(1-9) = -64
In both these cases x could be positive or negative since x^2 is always positive----INSUFF
St 2. (x^2-1)<0
x^2<1
Again the only information we get from this statement is that x is a fraction. X could again be positive or negative. Try plugging in x=1/2 and x=-1/2 and the above condition will hold----INSUFF
Combining 1 & 2
(x^2-1) is negative
Hence (1-x^2) is positive.
And n is negative. But we still don't know whether x is positive or negative. We just know that x is a fraction less than 1. Try plugging in 1/2 and -1/2 as values of x and the above condition will hold
Hence the answer should be E
Whats the OA??
St 1: n^3(1-x^3)<0
Now we can have two situations
If n is negative then x<1
Let n=-2, x=1/3
-8(1-1/9) = -64/9
But if n is positive x is an integer.
Let n=2 x=-3
8(1-9) = -64
In both these cases x could be positive or negative since x^2 is always positive----INSUFF
St 2. (x^2-1)<0
x^2<1
Again the only information we get from this statement is that x is a fraction. X could again be positive or negative. Try plugging in x=1/2 and x=-1/2 and the above condition will hold----INSUFF
Combining 1 & 2
(x^2-1) is negative
Hence (1-x^2) is positive.
And n is negative. But we still don't know whether x is positive or negative. We just know that x is a fraction less than 1. Try plugging in 1/2 and -1/2 as values of x and the above condition will hold
Hence the answer should be E
Whats the OA??
from onestubbornp wrote:20. Is x negative ?
(1)n^3(1-x^2)<0
(2)x^2-1<0
either n -ve and (1-x^2) +ve(x is a fraction)...a
or n is positive and /x/>1............b........insuff
......
from 2
x^2<1.. x can be +ve or -ve??..........insuff
both
x is a fraction however we still dont know if it is +ve or -ve thus insuff
E is my answer
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Ian Stewart
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stubbornp, where are these questions from? Surely it's supposed to read 'x^3', not 'n^3'; otherwise the OA is wrong.
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stubbornp
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I think so..There has a discrepency in the stimulus or in answer.Source is 1000 DS..Ian Stewart wrote:stubbornp, where are these questions from? Surely it's supposed to read 'x^3', not 'n^3'; otherwise the OA is wrong.
