Thread: Simple Question
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Old 10-10-2005, 02:29 PM
Tom1975 Tom1975 is offline
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Join Date: Jun 2005
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Default Re: Simple Question

[ QUOTE ]
For some reason I can't get the right answer for this.

Suppose a vase has 15 balls, of which 8 are red and seven are black.

In how many ways can 5 balls be chosen so that at least two are red?

[/ QUOTE ]

C(8,2)*C(7,3)+C(8,3)*C(7,2)+C(8,4)*C(7,1)+C(8,5)

This assumes it doesn't matter which order the balls are chosen.
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