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Tricky DS question.

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Tricky DS question.

by madhavi » Sat Nov 17, 2007 8:27 am
If a2 + b2 =13, what is the value of ab?



(1) (a + b)2 = 25.



(2) a(ab3) = 108.


Can't we solve (13-b2)b3=108? And will it not be Choice D?
The answer given is A.
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by ri2007 » Sat Nov 17, 2007 9:04 am
Its so easy to forget small rules of number properties.

any way statement 2 is

a(ab^3) = 108

so a^2 b^3 = 2^2 * 3^3

So b = 3 (OK)
but a = + or - 2

the statement in the stem will be satisfied with either values of a since it includes a a^2 but the question needs u to identify the value of a which can be negative or positive and this thus will give diff values for 2ab
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