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Thread: Counting question

  1. #1
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    Question Counting question




    4 selections of single digits are made at random with replacement, from the 10 digits 0-9. Find the probability that these sum to 20.

    I thought first that arrangement would matter but not too sure now, it might be a partition question. the 0 kind of messes things up

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    Re: Counting question


    For a problem of this size, I’d simply use a spreadsheet to enumerate all 10,000 possibilities (0000 to 9999) and to count the number of occurrences of 20 as the digit sum.

    This looks to be about five minutes’ work.

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