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Math Help - Probability Problem

  1. #1
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    Probability Problem

    A box contains 12 red and 13 white marbles. If 8 marbles are chosen at random (without replacement) determine the probability that 6 are red. Write your answer as a fraction reduced to lowest terms.

    PLease help! I thought I knew what to do but then I just kept confusing myself.
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  2. #2
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    Quote Originally Posted by sweeetcaroline View Post
    A box contains 12 red and 13 white marbles. If 8 marbles are chosen at random (without replacement) determine the probability that 6 are red. Write your answer as a fraction reduced to lowest terms.
    PLease help! I thought I knew what to do but then I just kept confusing myself.
    Why not show us what you have done that is confusing you?
    We cannot help if we are in the dark.
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  3. #3
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    Well I thought that I could use a binomial or geometic model, but that didn't take into account that of 8 chosen probability that 6 are red. And then I thought that maybe somehow using the number of possibilities, figure out how many that has 6 red if 8 are chosen but I wasn't exactly sure how to do that. Am I on the right track with either of these ideas?
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  4. #4
    MHF Contributor matheagle's Avatar
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    hypergeometric

    { {12\choose 6}{13\choose 2}\over {25\choose 8}}
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