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Thread: Postage Stamps Problem?

  1. #16
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    Re: Postage Stamps Problem?

    Look at the last digit:
    0 or 5 needs 0x11
    1 or 6 needs 1x11
    2 or 7 needs 2x11
    3 or 8 needs 3x11
    4 or 9 needs 4x11.
    39 is the biggest number that cannot be reached because 4x11 is 44.
    Thanks from kikhakplz
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  2. #17
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    Re: Postage Stamps Problem?

    Quote Originally Posted by kikhakplz View Post
    So i still have to do the counting rightay
    I was surprised by the fact that u went from 65-76-87-98
    Again, from your comments I cannot tell your level.So
    I gave you some pseudo code.
    Start with your target number $K$.
    Do a loop consisting of subtracting $11$ from $K$ until you get a multiple of five.
    Note that in the loop if $\left\lfloor {\frac{R}{5}} \right\rfloor = \frac{R}{5}$ then you have a multiple of five.
    That stops the loop & gives you the result. If that is still a mystery to you then please find a face to face sit-down help/
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  3. #18
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    Re: Postage Stamps Problem?

    This is the Diophantine Frobenius Problem

    If gcd(a,b)=1 then the number you are looking for is m=ab-a-b

    example

    a=5, b=11, m=39
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