Hello. I'm not sure if this question goes to algebra, calculus, or other place, and if it is, please let me know, I am willing to fix.

Here's my question. I have the following sets of numbers, and I need to find the formula to the question mark, so the formula is the same exact for all sets.

For example if ? = /1.56/100

Then that would wok for first set, but not the second, because 18/1.56/100 would equal .115 instead of .4

25 ? =0.16

18 ? =0.40

15 ? =0.5

10 ? =1