return a number between 3 to 5 by get a number between 1 until 10000!

Question

I want to have a math math formulas to do this operation:

A:get a number between 1 to 10000 B:reteun a number between 3.00 until 5 for example 3.89

for greater number return greater number too!

A:500 ---> 3.45 B:9000 ---> 4.70 C:10000 -->5

can anybody help me? I need it for a php algorithm.

Answer 1

One solution might be $f(x) = \frac{x}{5000}+3$.