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Thread: Permutations with restrictions

  1. #1
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    Permutations with restrictions

    Good evening ....

    my question is more conceptual than arithmetical.

    a given question says:
    Example 5 Cont.: How many 4-digits number can be formed out of 0,1,2,3,5,7 and 8. If:

    a: the number must be even with no repetition

    i understand that the answer here is 3 x (6 x 5 x 4)=360

    b: number must be even with repetition

    this is where i get confused.

    i under stand that the last digit will be 0 or 2 or 8

    now, if repetition is allowed, to me, it means that i can also use 0,2 and 8.

    which means the answer shd be 3 x 8^3

    however the answer uses 3 x 7^3

    can anyone explain why my reasoning is incorrect.

    thank u!!

  2. #2
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    Re: Permutations with restrictions

    Your reasoning is incorrect because there are only seven possibilities.
    I don't have emotions and sometimes that makes me very sad.

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