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Exponent problem: Please show me the easy way.....

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Exponent problem: Please show me the easy way..... [#permalink] New post 26 Oct 2011, 23:06
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Question Stats:

80% (01:37) correct 20% (00:56) wrong based on 59 sessions
What is greatest positive integer n such that 2^n is a factor of 12^10?

a)10
b)12
c)16
d)20
e)60

Please show me the easy way to solve such question...
[Reveal] Spoiler: OA

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Re: Exponent problem: Please show me the easy way..... [#permalink] New post 26 Oct 2011, 23:32
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aselfmademan wrote:
What is greatest positive integer n such that 2^n is a factor of 12^10?

a)10
b)12
c)16
d)20
e)60

Please show me the easy way to solve such question...


The given number is 12^10
=(2*2*3)^10
=(2^20)*(3^10)

So the greatest possible value for n such that 2^n can be factor of given number is 20.

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Re: Exponent problem: Please show me the easy way..... [#permalink] New post 27 Oct 2011, 04:02
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aselfmademan wrote:
What is greatest positive integer n such that 2^n is a factor of 12^10?

a)10
b)12
c)16
d)20
e)60

Please show me the easy way to solve such question...


\(12^{10} = (2^2*3)^{10} = 2^{20}*3^{10}\)
The greatest value of n such that \(2^n\) is a factor of \(12^{10}\) is 20.

Such questions are more popular and a little more complex with factorials. e.g. What is greatest positive integer n such that \(2^n\) is a factor of 12!
Try this one.
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Re: Exponent problem: Please show me the easy way..... [#permalink] New post 27 Oct 2011, 07:00
Thanks gopu106........ :)
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Re: Exponent problem: Please show me the easy way..... [#permalink] New post 27 Oct 2011, 07:03
VeritasPrepKarishma wrote:
aselfmademan wrote:
What is greatest positive integer n such that 2^n is a factor of 12^10?

a)10
b)12
c)16
d)20
e)60

Please show me the easy way to solve such question...


\(12^{10} = (2^2*3)^{10} = 2^{20}*3^{10}\)
The greatest value of n such that \(2^n\) is a factor of \(12^{10}\) is 20.

Such questions are more popular and a little more complex with factorials. e.g. What is greatest positive integer n such that \(2^n\) is a factor of 12!
Try this one.


Thank you very much.......... :-D I am very weak in this type of PS math :(
Could you please explain 12! math you have given ?
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Re: Exponent problem: Please show me the easy way..... [#permalink] New post 27 Oct 2011, 19:32
VeritasPrepKarishma wrote:
aselfmademan wrote:
What is greatest positive integer n such that 2^n is a factor of 12^10?

a)10
b)12
c)16
d)20
e)60

Please show me the easy way to solve such question...


\(12^{10} = (2^2*3)^{10} = 2^{20}*3^{10}\)
The greatest value of n such that \(2^n\) is a factor of \(12^{10}\) is 20.

Such questions are more popular and a little more complex with factorials. e.g. What is greatest positive integer n such that \(2^n\) is a factor of 12!
Try this one.



n = 10

I just counted the number of 2s till 12 since the 12! is multiplication of all numbers till 12


Do you have any faster method which can be used for bigger factorials?
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Re: Exponent problem: Please show me the easy way..... [#permalink] New post 27 Oct 2011, 19:39
Expert's post
Check out this post: http://www.veritasprep.com/blog/2011/06 ... actorials/

It discusses how to solve such questions quickly.
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Re: Exponent problem: Please show me the easy way..... [#permalink] New post 28 Oct 2011, 21:58
Thanksss :-D
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Re: Exponent problem: Please show me the easy way.....   [#permalink] 28 Oct 2011, 21:58
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