Question

explain why a change from 20 to 40 is 100% increase, but a change from 40 to 20 is a 50% decrease.

Answer 1

I think I'm starting to see it. 20 to 40 20 add 20 = 40 100% increased 40 to 20 40 divided by 20 = 2 half has been takin 50% off of 40 divided by 2.