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Math Help - premutation

  1. #1
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    premutation

    Evaluate P(7,3)

    what does the p stand for and how do i solve it? the question before it was evaluate 6! (720) so it might be along those lines but is this a typo?
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by andy11 View Post
    Evaluate P(7,3)

    what does the p stand for and how do i solve it? the question before it was evaluate 6! (720) so it might be along those lines but is this a typo?
    Judging by what your previous question asked, i think you want the permutation


    P(n,r) = \frac {n!}{(n - r)!}

    So, P(7,3) = \frac {7!}{(7 - 3)!} = \frac {7!}{4!} = 7(6)(5) = 210


    For the record, you may encounter these other notations in the future, so i'll tell them to you.

    P(n,r) = _n P _r = P_{r}^{n}
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  3. #3
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    P could stand for permutation: P(n,j) = \frac{{n!}}{{(n - j)!}} = n\left( {n - 1} \right)\left( {n - 2} \right) \cdots \left( {n - j + 1} \right)
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  4. #4
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    oh ok yeah thats the nCr key right?
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by andy11 View Post
    oh ok yeah thats the nCr key right?
    no, there is an nPr key. nCr is something different, it's what we call a "combination"
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  6. #6
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    ok yeah i know what you mean now.. thanks
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