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permutations

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Intern
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Joined: 07 Jun 2018
Posts: 5
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permutations   [#permalink]

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New post 18 Jul 2018, 06:54
There are four distinct pairs of brothers and sisters. In how many ways can a committee of 3 be formed and NOT have siblings in it?
a)8
b)24
C)32
d)56
e) 80

why is my approach wrong ?


My approach :

4C3 + 4C3 + (4C2 * 3C1) + (4C2 * 3C1)

selecting all brothers + all sisters + 2 brothers and 1 sister of 3 + 2 sisters and 1 brother of 3.

solution : 32

Sent from my SM-G955F using GMAT Club Forum mobile app
Senior Manager
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Joined: 12 Feb 2015
Posts: 373
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Re: permutations  [#permalink]

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New post 18 Jul 2018, 08:29
Discussed here:-

https://gmatclub.com/forum/if-there-are ... 99992.html

Hope it helps!!
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Re: permutations &nbs [#permalink] 18 Jul 2018, 08:29
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