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Question on combinations

  1. Aug 27, 2014 #1
    1. The problem statement, all variables and given/known data

    We need to select 5 committee members form a class of 70 students.
    • How many possible samples exists?
    • How many possible samples exists if the committee members all have different roles?

    2. Relevant equations

    nCr = n! / (r!(n-r)!)

    3. The attempt at a solution

    I am able to solve the first part.
    "How many possible samples exists?" = 70C5

    But I am unsure of the second.
    Would it simply be:
    70C1 x 69C1 x 68C1 x 67C1 x 66C1 x 65C1
     
  2. jcsd
  3. Aug 27, 2014 #2
    Second part is very close. I think you understand it but made a mistake when writing it down.
     
  4. Aug 27, 2014 #3
    My mistake, 65C1 should not be there.
     
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