Trying to define relationship between two numbers

Question

I have 2 numbers 97 (F) and 415 (S) this is the key / legend.

Given any number (S), commonly between 200 - 900, I am looking for "F".

Where if (S) is above 415 "F" will be less than 97 and if (S) is below 415 "F" will be more than 97.

• The higher "S" is the lower "F" is.
• The lower "S" is the higher "F" is.

Here's some estimations:

• 415 (S) gives 97 (F)
• 612 (S) should give ~72 (F)
• 514 (S) should give ~82 (F)

This is not a standard proportion as (F) of 612 (S) would be higher than 97.

What is this relationship called? How can I find the "F" of any number (S)?

Answer 1

I believe I figured this out by doing this.

const getF = (S) => (1 / (S / 415)) * 97;