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Junior | Next Rank: 30 Posts
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by Gdieterling » Thu Sep 03, 2009 11:28 am
Hello guys,

This one had me wondering, as I thought it was an easy one (the first question I had on the GMAT prep Cat):

2^(4-1)^2 / 2^(3-2) = ?

2^8
2^7
2^6
2^5
2^4

I thought this was D, but the OA is A.

Can someone explain ?
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by bdoug » Thu Sep 03, 2009 12:02 pm
First do the simple subtraction contained in the exponents to get: 2^(3)^(2)/2^(1)

3^2 = 9, so 2^3^2 = 2^9 and our original problem becomes: 2^9 / 2^1 or 2^9 / 2

2^9 / 2 becomes 2^8 when you cancel out the 2 in the denominator with one of the 2's from 2^9.

Remember also that 2^9/2^1 is the same as [2^(9)]*[2^(-1)] or 2^(9-1) which equals 2^8 !
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Junior | Next Rank: 30 Posts
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by Gdieterling » Thu Sep 03, 2009 12:24 pm
Thanks for the answer !

However, isn't it supposed to be :

2^(4-1)^2 = 2^(3)^2 = 2^(3*2) = 2^6 ?

I'm confused !


EDIT :

Ok, think I got it, it's coming from the bracket :

(2^(4-1))^2 = 2^6
2^(4-1)^2 = 2^9

Thanks again :)
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