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# GMATPREP:Permutaion & combination

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VP
Joined: 18 May 2008
Posts: 1200

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29 Jan 2009, 04:18

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SVP
Joined: 17 Jun 2008
Posts: 1502

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29 Jan 2009, 05:30
It will be 26 + (26*26) + (26*26*26)
= 18278
SVP
Joined: 07 Nov 2007
Posts: 1756
Location: New York

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29 Jan 2009, 08:30
1
KUDOS
scthakur wrote:
It will be 26 + (26*26) + (26*26*26)
= 18278

Same approach.

just my 2 cents.. no need to calculate/multiple..
26 + (26*26) + (26*26*26) --> all these end with unit digit 6.
SUM OF THESE THREE NUMBERS must be NUMBR with unit digit 8
only one option available.
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VP
Joined: 18 May 2008
Posts: 1200

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29 Jan 2009, 10:33
+1 for this shortcut.
x2suresh wrote:
scthakur wrote:
It will be 26 + (26*26) + (26*26*26)
= 18278

Same approach.

just my 2 cents.. we no need to calculate/multiple..
26 + (26*26) + (26*26*26) --> all these end with unit digit 6.
so sum's last digit must be 8 only one option available.
Director
Joined: 01 Apr 2008
Posts: 846
Name: Ronak Amin
Schools: IIM Lucknow (IPMX) - Class of 2014

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01 Feb 2009, 07:00
So..one thing to note here...may be people already know.

Permutation formula nPr = n! / (n-r)! doesnt consider repetitions

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Re: GMATPREP:Permutaion & combination   [#permalink] 01 Feb 2009, 07:00
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# GMATPREP:Permutaion & combination

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