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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
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A dancing class consists of 5 boys and 4 girls. How many [#permalink]  14 Dec 2007, 19:23
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, 19:39, edited 1 time in total.
Director
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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
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5*4 = 20 different pairs
Director
Joined: 11 Jun 2007
Posts: 649
Followers: 3

Kudos [?]: 82 [0], given: 0

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
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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
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