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Homework Help: Probabaility of having certain number of parents in a committee

  1. Jul 8, 2014 #1
    1. The problem statement, all variables and given/known data

    A committee of 5 members is formed from 6 parents , 2 teachers, and a principal, In how many ways, can this committee be formed if the committee consists of not more than 4 parents?

    my working is 1 parent + 2 parents + 3 parents +4 parents

    which is (6C1 x 8C4) + (6C2 x 7C3) +(6C3x 6C2)+ (6C4 x 5C1)

    but the ans given is only 120

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jul 8, 2014 #2


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    Since there are only 3 non-parents your choices for number of parents are 2,3, and 4. Once you have counted the parents, the others must be chosen from the non-parents. Try again.
  4. Jul 8, 2014 #3

    Ray Vickson

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    Does the identities of the parents and teachers matter? In other words, would a 3-parent committee having parents Smith, Jones and Chakravarty be counted separately from a 3-parent committee having parents Smith, Jones and Salam? Ditto for the teachers.
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