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Homework Help: How do u solve for n Permutations

  1. May 6, 2005 #1
    how do u solve for n?
    nP3=720........n!/(n-3)!=720.....do u just start cancelling?
    that will be n(n-1)(n-2)=720...but its such a big number...is there another easier way to do it?
  2. jcsd
  3. May 6, 2005 #2


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    Science Advisor

    Factor 720 to help find the solution:
    720 = (24)*(32)*(5) = n*(n - 1)*(n - 2) = (???)*(???)*(???)
    (Hint: Try 23)

    Last edited: May 6, 2005
  4. May 6, 2005 #3
    by cancelling do you mean use the factor theorem? because i would expand and move the 720 to the left side and factor it out
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