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Did this on the GMATprep - and I swear I got it right, but

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What do you think the answer is?

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Manager
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Did this on the GMATprep - and I swear I got it right, but [#permalink] New post 25 Aug 2007, 18:35
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Did this on the GMATprep - and I swear I got it right, but the original answer suggests differently.

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

A. 2^8
B. 2^7
C. 2^6
D. 2^5
E. 2^4

I'm convinced that my answer is D (highlight to see)

But the OA is A (highlight to see)...
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Re: Question on exponentials [#permalink] New post 25 Aug 2007, 19:36
Big-O wrote:
Did this on the GMATprep - and I swear I got it right, but the original answer suggests differently.

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

A. 2^8
B. 2^7
C. 2^6
D. 2^5
E. 2^4

I'm convinced that my answer is D (highlight to see)

But the OA is A (highlight to see)...


You can think of this two way, which are totally different. Let's just consider the top part...
2^(4-1)^2
This can be seen as: (2^3)^2 = 2^6
OR
2^(3^2) = 2^9
The latter will give you the right answer. I imagine in GMATprep, it should be pretty clear. Do you have a snapshot of the problem?
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 [#permalink] New post 25 Aug 2007, 20:38
Here is the screenshot (I haven't been around enough to directly hotlink

A^B^C is the same as A^BC, therefore the top gives 2^6, not 2^9...
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 [#permalink] New post 25 Aug 2007, 21:09
edited post :(

Its a simple case of BEDMAS

http://www.answers.com/BEDMAS

2^3^2 = 2^(3^2) = 512

not (2^3)^2 = 64

Don't check this in Excel spreadsheet. Excel will yield 64 for 2^3^2 this is wrong !

:-D

Last edited by KillerSquirrel on 25 Aug 2007, 23:49, edited 2 times in total.
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 [#permalink] New post 25 Aug 2007, 21:14
Thanks for the shot. I would have get 2^9 for the top, but I agree it is a bit unclear.
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 [#permalink] New post 25 Aug 2007, 22:43
see edited post above !

:-D

Last edited by KillerSquirrel on 25 Aug 2007, 23:48, edited 1 time in total.
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 [#permalink] New post 25 Aug 2007, 22:47
KillerSquirrel wrote:
bkk145 wrote:
Thanks for the shot. I would have get 2^9 for the top, but I agree it is a bit unclear.


please explain !

:-D


I see the operation of (4-1)^2 = 9 first.
Otherwise, I feel that there should have been parenthesizes like this:
(2^(4-1))^2
  [#permalink] 25 Aug 2007, 22:47
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Did this on the GMATprep - and I swear I got it right, but

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