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Math Help - coprime numbers

  1. #1
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    coprime numbers

    2m-3 and 10m-15 are coprime integers.Which of the choices from below
    is coprime with each one of the numbers?
    a)3m-1
    b)m+4
    c)2m+6
    d)m+3
    e)5m
    Answer is b.

    I couldn't find the answer.
    First of all both numbers are not coprime. When we divide them with
    each other we get 5 or 1/5.
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  2. #2
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    Re: coprime numbers

    10m-15 = 5(2m-3), so the second is a multiple of the first. I agree they are not coprime.
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  3. #3
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    Re: coprime numbers

    in order for 2m-3 and 10-15=5(2m-3) to be coprime m=2.

    Thus we have 1 and 5 as our two numbers. The values corresponding to the answers are

    a)5
    b)6
    c)10
    d)5
    e)10

    and clearly of these only 6 is coprime to to 5 so (b) must be the answer.
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  4. #4
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    Re: coprime numbers

    many thanks
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