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Small piece of probability

  1. Nov 24, 2007 #1
    1. The problem statement, all variables and given/known data

    A club for 18 members, among them Frank. They'll pick out a komitee of 5 members.
    (a. How many different komitees is produced? Easy, just the binom. 18 over 5.)

    b, How many if Franks in? (The question)

    2. Relevant equations

    (Unarranged sortments with no takebacks)
    binominalkoefficient nCr:
    ( p )
    ( r )
    ((p over r))

    3. The attempt at a solution

    18 over 5 minus 17 over 5?? No.
     
  2. jcsd
  3. Nov 24, 2007 #2
    for b. if Frank is always in, you have to choose only 4 members among the remaining 17, which is C[tex]^{17}_{4}[/tex], equivalent to your 18 over 5 minus 17 over 5.
     
    Last edited: Nov 24, 2007
  4. Nov 25, 2007 #3
    ah, 17C4, thanks a bunch.
     
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