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must be true question

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by neelgandham » Mon May 21, 2012 12:41 am
Hey there!(I love the username. Eliminates redundancy!)

If abc = b^3, which of the following must be true?
Assumption: In red.

abc = b^3
abc - b^3 = 0
b*(ac-b^2) = 0
So, ac = b^2 OR b = 0
I. ac = b^2 - Not necessarily true as the value of b can be 0.
e.g. If a = 3, b = 0 and c = 4, they satisfy the condition abc = b^3(3*4*0=0^3) but ac != b^2(12 != 0)
II. b = 0 - Not necessarily true as the value of b can be Square root(ac).
e.g. If a = 4, b = 4 and c = 4, they satisfy the condition abc = b^3(4*4*4=4^3) but b is not equal to 0.
III. ac = 1 - From the above we know that ac can be (From I: ac = 3*4 = 12 and From II: ac = 4*4 = 16 ))

IMO A or 1
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by GmatKiss » Tue May 22, 2012 3:23 am
IMO: A
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