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# A committee of 4 boys and 3 girls is to be formed by lots

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Intern
Joined: 29 Aug 2003
Posts: 29
Location: Mumbai
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A committee of 4 boys and 3 girls is to be formed by lots [#permalink]  10 Dec 2003, 05:16
A committee of 4 boys and 3 girls is to be formed by lots from 8 boys and 5 girls. One of the boys is brother of one of the girls. Find the probability that both are included in the committee.
Director
Joined: 13 Nov 2003
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Location: BULGARIA
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7C3*4C2/8C4*5C3=3/10...
Senior Manager
Joined: 23 Sep 2003
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Why 4C2 when you say 7C3*4C2?

I can understand 7C3 for selecting the brother but why don't you multiply this by 2C1 (ways of selecting the remaining 2 girls after you select the sister)?
Senior Manager
Joined: 23 Sep 2003
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Location: US
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I'm so dumb. Finally got it.

It's funny how your brain shuts down when it comes to basic stuff.

No wonder the GMAT constantly devours.
CEO
Joined: 15 Aug 2003
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Re: Probability!!! [#permalink]  13 Dec 2003, 00:39
4128851 wrote:
A committee of 4 boys and 3 girls is to be formed by lots from 8 boys and 5 girls. One of the boys is brother of one of the girls. Find the probability that both are included in the committee.

so..we say 2 are already selected.

remaining... select 3 boys and 2 girls from 7 boys and 5 girls

ways to select = 7C3 * 4C2 = 210

total ways to select the people = 8C4 * 5C3 = 700

PROB = 210 /700 = 3/10
Re: Probability!!!   [#permalink] 13 Dec 2003, 00:39
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