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Math Help - quick question

  1. #1
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    quick question

    say a pin number is 5 digits long. The pin number must have one 2 in it anywhere in the pin. How many different combinations can there be?

    I believe that there will be 16*10^4 but im not quite sure.

    also another one, how many combinations can there be if the 5 digit pin number can only have even digits? I think 5^5, not so sure either though.

    thanks.

    and one i haven't quite thought about, an even number of even digits. zero even numbers count.
    Last edited by ihaveamathproblem; November 24th 2007 at 08:12 PM.
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by ihaveamathproblem View Post
    say a pin number is 5 digits long. The pin number must have one 2 in it anywhere in the pin. How many different combinations can there be?

    I believe that there will be 16*10^4 but im not quite sure.
    The number containing no 2's is 9^5, the total number is 10^5 so the
    number with at least one 2 is (10^5-9^5).

    RonL
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  3. #3
    Grand Panjandrum
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    Quote Originally Posted by ihaveamathproblem View Post

    also another one, how many combinations can there be if the 5 digit pin number can only have even digits? I think 5^5, not so sure either though.
    th
    There are 5 even digits 0, 2, 4, 6, 8. So the number of pins consisting only
    of these digits is 5^5.

    RonL
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  4. #4
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    thank you very much captain black.
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