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Carloblacksun
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 Posted: Thu Nov 20, 2008 1:07 pm Post subject: Stupid Committees |
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If there are 16 people to choose from, what is the ratio of the number of possible 7-person committees to the number of possible 8-person committees?
A) 7:8
B) 8:7
C) 7:9
D) 8:9
E) 9:8
I found this question on some material downloadable from this website...
ciao ciao!! |
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earth@work
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| Posted: Thu Nov 20, 2008 2:00 pm Post subject: |
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IMO : (D) 8:9
16C7 :16C8 = 16C7/16C8 = 8/9 |
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mals24
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| Posted: Thu Nov 20, 2008 2:08 pm Post subject: |
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Agree with earth@work Answer should be D
16C7 = 16!/(7!*9!) = 4*5*2*13*2*11
16C8 = 16!/(8!*8!) = 2*5*13*11*9
16C7/16C8 = 8/9. |
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Carloblacksun
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| Posted: Thu Nov 20, 2008 2:10 pm Post subject: |
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it's right!!
I used the wrong formula...this is why!! thanks a lot!! |
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logitech
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| Posted: Thu Nov 20, 2008 2:11 pm Post subject: |
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NCK = NC(N-K)
For example:
16C7 = 16C9
It can be useful!
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Logitech
2009 is not a prime number! |
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