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Math Help - permutation problem

  1. #1
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    Lancaster, Ohio
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    permutation problem

    How many permutations of the digits 0, 1, 2, . . . , 9 either start with a 3 or end with a 7?

    I thought the answer would be 9!+9! but the answer key states it is 9!+9!-8!

    what is the -8!




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  2. #2
    Junior Member
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    Hyrule
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    Re: permutation problem

    Because you have counted two times the permutations which start with 3 and end with 7 simultaneously.
    Thanks from wattskickin
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