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Math Help - Permutations

  1. #1
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    Permutations

    How many three letter combinations can be formed from the letters "defgh" if no letter can be used more than once.

    I think this is the answer:

    P(5!, 3!) = 5!/3! = 5 * 4 * 3! * 2!/3! * 2! = 5 * 4 = 20

    Is this right?
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  2. #2
    Eater of Worlds
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    If order matters, then P(5,3)=60.

    If order doesn't matter, then C(5,3)=10

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

    C(n,k)=\frac{n!}{(n-k)!k!}
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