Suppose there are 19 marbles in a bag: 5 red, 6 green, and 8 blue ones. How many ways can 5 marbles be selected if exactly 2 marbles are red and 3 are another color?
How do I remove repetitions from a combinatorics problem?
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combinatorics
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0Maybe, it's also good to ask, whether OP is aware of the [principle of inclusion-exclusion](http://en.wikipedia.org/wiki/Inclusion–exclusion_principle)? – 2012-01-18
1 Answers
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This is a simple problem, and you don't need inclusion-exclusion, removing repetitions, and the like.
# of ways = (ways to select 2 red)*(ways to select any 3 of other colors)
= C(5,2)*C(14,3)
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0@JavaMan: Ok, i'm new to this forum. I'll bear it in mind. – 2012-01-18