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2^(4-1)^2/ 2^(3-2)= a) 2^8 b) 2^7 c) 2^6 d) 2^5 e) 2^4

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2^(4-1)^2/ 2^(3-2)= a) 2^8 b) 2^7 c) 2^6 d) 2^5 e) 2^4 [#permalink] New post 07 Jan 2009, 16:52
2^(4-1)^2/ 2^(3-2)=

a)2^8
b) 2^7
c)2^6
d) 2^5
e) 2^4

Please show work as I got this answer wrong.
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Re: GMATPrep - Exponents [#permalink] New post 07 Jan 2009, 17:49
Bluepic wrote:
2^(4-1)^2/ 2^(3-2)=

a) 2^8
b) 2^7
c) 2^6
d) 2^5
e) 2^4

Please show work as I got this answer wrong.



= 2^(4-1)^2 / 2^(3-2)
= 2^(3)^2 / 2
= 2^6 / 2
= 2^5
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Re: GMATPrep - Exponents [#permalink] New post 07 Jan 2009, 18:07
That's the same answer I came up with but that is incorrect. I wonder if there is an error in GMATPrep.

I also need to correct a paranthesis in the way I wrote the original question; I don't think this changes anything though.

2^(4-1)^2/2^3-2
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Re: GMATPrep - Exponents [#permalink] New post 07 Jan 2009, 18:08
I may be wrong; but this is how I solved it:
2^(4-1)^2/2^(3-2)
=2^3^2/2=2^9/2=2^8.
GMAT TIGER wrote:
Bluepic wrote:
2^(4-1)^2/ 2^(3-2)=

a) 2^8
b) 2^7
c) 2^6
d) 2^5
e) 2^4

Please show work as I got this answer wrong.



= 2^(4-1)^2 / 2^(3-2)
= 2^(3)^2 / 2
= 2^6 / 2
= 2^5
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Re: GMATPrep - Exponents [#permalink] New post 07 Jan 2009, 18:10
tusharvk, you're answer is correct.

Can you explain why yours is correct and GMAT Tiger is not; I agreed with GMAT Tiger's reasoning but it was the incorrect answer choice.
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Re: GMATPrep - Exponents [#permalink] New post 07 Jan 2009, 18:29
bluepic my answer is based on
c=a^x^y then b=a^x and c=b^y.
Bluepic wrote:
tusharvk, you're answer is correct.

Can you explain why yours is correct and GMAT Tiger is not; I agreed with GMAT Tiger's reasoning but it was the incorrect answer choice.
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Re: GMATPrep - Exponents [#permalink] New post 07 Jan 2009, 19:40
tusharvk wrote:
I may be wrong; but this is how I solved it:
2^(4-1)^2/2^(3-2)
=2^3^2/2=2^9/2=2^8.
GMAT TIGER wrote:
Bluepic wrote:
2^(4-1)^2/ 2^(3-2)=

a) 2^8
b) 2^7
c) 2^6
d) 2^5
e) 2^4

Please show work as I got this answer wrong.



= 2^(4-1)^2 / 2^(3-2)
= 2^(3)^2 / 2
= 2^6 / 2
= 2^5



2^3 raised to 2 is not equal to 9! I think that is incorrect.
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Re: GMATPrep - Exponents [#permalink] New post 07 Jan 2009, 19:59
tusharvk has considered 2 to be the base and (4-1)^2 to be the exponent.

Gmattiger has considered 2^(4-1) to be the base and 2 to be the exponent.

tusharvk is correct.
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Re: GMATPrep - Exponents [#permalink] New post 07 Jan 2009, 21:03
GMAT TIGER wrote:
Bluepic wrote:
2^(4-1)^2/ 2^(3-2)=

a) 2^8
b) 2^7
c) 2^6
d) 2^5
e) 2^4

Please show work as I got this answer wrong.



= 2^(4-1)^2 / 2^(3-2)
= 2^(3)^2 / 2
= 2^6 / 2
= 2^5


I thought that way (2^8) too but ended with 2^5 because I remember a question: If X=10^100 , X^X = 10^K. What is K= ?

The following notes are by walker:
Quote:
(x^y)^z=x^(y*z) - is a key point. There are no any other additional formula.

more examples:

(2^3)^5=8^5=32768 or
(2^3)^5=2^(3*5)=2^15=2*2^14=2*4^7=2*4*4^6=8*16^3=32768 or
(2^3)^5=2^(3*5)=(2^5)^3=32^3=32768

√x=4. What is x^3?
x^3=x^(3*2*1/2)=x^(6*1/2)=(x^1/2)^6=(√x)^6=4^6

in the case of (10^100)^(10^100):

(10^100)^(10^100)=10^(100*(10^100)) = 10^(10^2*(10^100)) = 10^(10^(2+100))) = 10^(10^102)=10^k ==> k=10^102


How one should relate this problem with the above notes:

when is 2^(4-1)^2 = 2^6 and when is 2^(4-1)^2 = 2^9?
any clear rule?
thanks
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Re: GMATPrep - Exponents [#permalink] New post 08 Jan 2009, 03:26
You are assuming that 2^3^2 is the same as (2^3)^2 which is not correct
In my opinion the answer is 2^8
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Re: GMATPrep - Exponents [#permalink] New post 08 Jan 2009, 07:32
OP please provide the snapshot of the orignial question by print screen or some other means. I appreciate it. It will then be clear whether it is

a^b^c or a^(b*c)

Thank you.
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Re: GMATPrep - Exponents [#permalink] New post 08 Jan 2009, 07:47
the question is not clear. Because power raised by the power you multiply the powers. If power times power, you add powers. Print screen and upload, pls.
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Re: GMATPrep - Exponents [#permalink] New post 08 Jan 2009, 07:48
tusharvk wrote:
OP please provide the snapshot of the orignial question by print screen or some other means. I appreciate it. It will then be clear whether it is

a^b^c or a^(b*c)

Thank you.


......or use the formula option...
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Re: GMATPrep - Exponents [#permalink] New post 08 Jan 2009, 08:20
I did this in excel.

2^3^2 = 64 = 2^6

2^(3^2) = 512 = 2^9

The numerator of the stated question is in the 2^3^2 format. Not sure how the answer cannot be 2^5.
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Re: GMATPrep - Exponents [#permalink] New post 08 Jan 2009, 08:51
See attached for print screen.
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GMATPrep Exponent.doc [51.5 KiB]
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Re: GMATPrep - Exponents [#permalink] New post 08 Jan 2009, 08:52
I finally found it in GMATPrep. It is the easiest question ever. All the confusion because the question wasn't printed clearly. It goes like that:
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power problem.jpg
power problem.jpg [ 40.57 KiB | Viewed 654 times ]

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Re: GMATPrep - Exponents [#permalink] New post 08 Jan 2009, 09:07
linau1982 wrote:
I finally found it in GMATPrep. It is the easiest question ever. All the confusion because the question wasn't printed clearly. It goes like that:


there is no clear evidence here that 2 is the base and (4-1)^2 is the exponent. I still think GMATprep got it wrong.
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Re: GMATPrep - Exponents [#permalink] New post 08 Jan 2009, 09:42
vscid wrote:
linau1982 wrote:
I finally found it in GMATPrep. It is the easiest question ever. All the confusion because the question wasn't printed clearly. It goes like that:


there is no clear evidence here that 2 is the base and (4-1)^2 is the exponent. I still think GMATprep got it wrong.


what do you mean by no clear evidence? According to what I see, it is completely clear that 2 is a base in both numerator and denominator and the rest of the numbers are powers
no offence :-D
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Re: GMATPrep - Exponents [#permalink] New post 08 Jan 2009, 16:19
yes. (4-1)^2 = 9 and therefore the answer is 2^8.
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Re: GMATPrep - Exponents [#permalink] New post 08 Jan 2009, 17:10
if we write this it equals: ( (2^3) * (2^3) ) / 2
= (8 * 8) /2
= 32

So I don't get how the answer is 2^9. Are you sure of the OA?
Re: GMATPrep - Exponents   [#permalink] 08 Jan 2009, 17:10
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