Slider with numbers

So i got the slider itself working, but how would I, for example with a slider length of 1 to 100 pixels create an array of numbers between 20 and 200? (or simply between numbers x and y)?

I figure theres tutorials all over the web for a formula, and that theres even a simple 9th grade math equation for it, but im simply too lazy.

Thanks in advance for any help…