Verify an approximation computed on an integer-arithmetic system

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Suppose a system which supports only integer-division, and is bounded by the range $[0,M]$.

Given positive integers $x$, $n$, $d$ and $K$, let the following be:

  • $y = \min(n,x)$
  • $z = \max(n,x)$
  • $p = \lfloor\frac{z}{K}\rfloor$
  • $q = \lfloor\frac{d}{K}\rfloor$

I know that:

  • $yp\leq M$
  • $xn>M$ and therefore cannot be computed directly

How can I determine whether or not $\lfloor\frac{yp}{q}\rfloor\leq\lfloor\frac{xn}{d}\rfloor$?

Thank you!

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Well in general, a floating-point division can be done with integer functions. Here is a numerical example:

125 / 13 = 9 <-

125 Mod 13 = 8

80 / 13 = 6 <-

80 Mod 13 = 2

20 / 13 = 1 <-

20 Mod 13 = 7

70 / 13 = 5 <-

for 9.615 as 9.62 .