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Source: — Data Sufficiency |
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by pemdas » Thu May 19, 2011 12:22 am
x^4 is positive, the fact that x is greater than another positive value means that original x raised to the power power of 4 was also positive. So we are left with new option x>0 and x^4 <x in statement (1) which is Sufficient. We can answer Yes, x is between 0 and 1.
in statement (2) x raised to the odd power is still positive, BUT we don't know the range and value of x-hence Not Sufficient

it must be a
Deepthi Subbu wrote:Is x between 0 and 1?

x4 < x
x5 > 0

I chose C but the answer was A . Can someone explain ?
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by sanju09 » Thu May 19, 2011 12:40 am
Deepthi Subbu wrote:Is x between 0 and 1?

x4 < x
x5 > 0

I chose C but the answer was A . Can someone explain ?

(1) Since x^4 < x » x^4 - x < 0 » x (x^3 - 1) < 0 » either x > 0 and x^3 - 1 < 0 or x < 0 and x^3 - 1 > 0 (which is impossible), and hence x > 0 and x^3 - 1 < 0 is true which gives

0 < x < 1. Sufficient

(2) If x^5 > 0 then x > 0 and we don't know how big or small a positive number is x. [spoiler]Insufficient

A[/spoiler]
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by Deepthi Subbu » Thu May 19, 2011 12:59 am
I now realise my mistake . I compared (-0.1) ^ 4 to 0.1 . Thanks pemdas and sanju09 .
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