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Math Help - Any methods on solving this

  1. #1
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    Question Any methods on solving this

    If each of the 10 digits is chosen at random, how many ways can you choose the following numbers?

    A)A two-digit code number repeated digits permitted
    B)A Three digit identification card number, for which the first digit cannot be a 0.

    If can answer at least one that would be great and thanks.
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  2. #2
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    Hello Shadows

    Welcome to Math Help Forum!
    Quote Originally Posted by Shadows View Post
    If each of the 10 digits is chosen at random, how many ways can you choose the following numbers?

    A)A two-digit code number repeated digits permitted
    B)A Three digit identification card number, for which the first digit cannot be a 0.

    If can answer at least one that would be great and thanks.
    A) There are 10 ways of choosing the first digit, and 10 ways of choosing the second digit. So there are 10\times10=100 ways of choosing the two digits, one after the other. (The codes are, of course, from 00 to 99 inclusive.)

    B) There are only 9 choices for the first digit, followed by 10 for each of the other two digits. So there are 9\times10\times10=900 possible choices altogether.

    Grandad
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