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Math Help - Number system question

  1. #1
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    Number system question

    Q. If 653xy is divisible by 80 then find the value of x+y.

    80 = 8 * 10

    So y = 0 (As it is divisible by 10)

    Now 3x0 should be divisible by 8. X can be both 2 and 6.

    The answer is 6. As per my calculation it can be both 2 and 6. Am i right ?
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  2. #2
    MHF Contributor alexmahone's Avatar
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    Quote Originally Posted by vivek_master146 View Post
    Q. If 653xy is divisible by 80 then find the value of x+y.

    80 = 8 * 10

    So y = 0 (As it is divisible by 10)

    Now 3x0 should be divisible by 8. X can be both 2 and 6.

    The answer is 6. As per my calculation it can be both 2 and 6. Am i right ?
    65320 is not divisible by 80.
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  3. #3
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    Quote Originally Posted by vivek_master146 View Post
    Q. If 653xy is divisible by 80 then find the value of x+y.

    80 = 8 * 10

    So y = 0 (As it is divisible by 10)
    That's correct.

    Now 3x0 should be divisible by 8. X can be both 2 and 6.

    The answer is 6. As per my calculation it can be both 2 and 6. Am i right ?
    If you have divided 653x0 by 10 you are left with 653x.

    Therefore 53x must be divisible by 8.
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