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Math Help - Is the answer provided wrong!?

  1. #1
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    Is the answer provided wrong!?

    Calculate the number of even numbers between 5000 and 7000 which can be formed from the digits 1,5,6 and 8 if repetitions are allowed.
    I tried working on this question a few times and came to 48 but, the answer given is 60. Can anyone help me??? Thank you!
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  2. #2
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    Hello cyt91
    Quote Originally Posted by cyt91 View Post
    Calculate the number of even numbers between 5000 and 7000 which can be formed from the digits 1,5,6 and 8 if repetitions are allowed.
    I tried working on this question a few times and came to 48 but, the answer given is 60. Can anyone help me??? Thank you!
    I don't get either of these answers; I reckon it's 64. As follows:
    The first digit is 5 or 6. So there are 2 choices here.

    The second and third digits can be any one of 4; so that's 4^2 choices.

    The final digit must be 6 or 8: 2 choices.
    So the total number of choices, and hence the total number of numbers is:
    2\times4^2\times2=64
    Grandad
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  3. #3
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    Quote Originally Posted by cyt91 View Post
    Calculate the number of even numbers between 5000 and 7000 which can be formed from the digits 1,5,6 and 8 if repetitions are allowed.
    I tried working on this question a few times and came to 48 but, the answer given is 60. Can anyone help me??? Thank you!
    I'm getting 64

    5--6 in the middle both equal........ 4 choices
    5--6 in the middle both different... .4(3)=12 choices
    5--8 in the middle both equal.........4
    5--8 in the middle both different.....12
    6--6 in the middle both equal.........4
    6--6 in the middle both different.....12
    6--8 in the middle both equal..........4
    6--8 in the middle both different.....12
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  4. #4
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    Thanks a lot. I've worked it out again. It is 64. Appreciate this!
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