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Finding combinations in an urn model

  1. Oct 4, 2008 #1
    Hi, this is my first post on this forum, i hope you can help. I seem to have confused my self with the following problem.

    Given an urn with R red balls and B blue balls and R+B = N, and N is always even. You remove the two balls at a time from the urn until it is empty - the without replacement case.

    a) what is the probability of some i (r, b) pairs. for example, given R=4 and B=8, what probability of the set containing 2 {r, b} pairs, i.e {r, b}, {r, b}, {r, ,r}, {b,b}, {b,b}, {b,b}

    b) what is the probability of each set that contains at least one {r,b} pair.

    thanks for your help.
  2. jcsd
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