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# A dancing class consists of 5 boys and 4 girls. How many

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Director
Joined: 11 Jun 2007
Posts: 637
A dancing class consists of 5 boys and 4 girls. How many [#permalink]

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14 Dec 2007, 20:23
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

A dancing class consists of 5 boys and 4 girls. How many different boy-girl pairs are possible?

Last edited by eyunni on 14 Dec 2007, 20:39, edited 1 time in total.
Director
Joined: 11 Jun 2007
Posts: 637

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14 Dec 2007, 20:48
bmwhype2 wrote:
20.

Does the question mean how many single pairs? I thought there could be multiple pairs. For example, 1 boy out of 5 and 1 girl out of 4. Then from the 4 boys and 3 girls, 1 more pair and so on...
Director
Joined: 12 Jul 2007
Posts: 858

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14 Dec 2007, 22:11
5*4 = 20 different pairs
Director
Joined: 11 Jun 2007
Posts: 637

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15 Dec 2007, 05:53
eyunni wrote:
bmwhype2 wrote:
20.

Does the question mean how many single pairs? I thought there could be multiple pairs. For example, 1 boy out of 5 and 1 girl out of 4. Then from the 4 boys and 3 girls, 1 more pair and so on...

Can someone please explain my question? I posted this not just for the answer. Thanks.
Intern
Joined: 13 Jun 2007
Posts: 48

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15 Dec 2007, 06:47
i think i get what you mean but i might be totally wrong on this one...

So here goes:

Start with 5 boys and 4 girls in how many different sets of 4 pairs.
5 different sets of (4 boys and 4 girls in 4 pairs)
5 different sets of (16 different pairs of which you select 4 pairs)
5x16C4=4*(16*15*14*13/(4*3*2))=5*4*5*7*13=....

Hope this helps
15 Dec 2007, 06:47
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