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Generalize (Posted on 2013-05-01) Difficulty: 3 of 5
Using only 4$ and 7$ bills, you could pay any integer number of dollars, greater than 17.
Prove it.

Given two coprime numbers a and b, what is the minimal number M(a,b) such that any amount greater or equal to M(a,b) can be expressed as p*a+q*b (p & q non-negative integers)?

How much is M(37,38)?

No Solution Yet Submitted by Ady TZIDON    
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re(2): part 1 solution, plus examples of M(x,y) | Comment 3 of 5 |
(In reply to re: part 1 solution, plus examples of M(x,y) by Charlie)

a*b-a-b+1 = (a-1)*(b-1), which I find is computationally easier

Edited on May 1, 2013, 8:01 pm
  Posted by Steve Herman on 2013-05-01 19:59:16

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