I hope this wasn´t asked before, and if it was I wouldn´t know which search terms to use. Hence, my appologies if the answer is already here somewhere.
If I have two numbers, let´s say 2 and 10, and I want to know the percentage of difference between them if starting at 2, it´s 10-2/(2/100) = 400. But, if I only know the number 400, and not 2 and 10, is there a way that I can use the number 400 to conclude that the percentage between the two numbers, if starting at 10 so 10-2/(10/100) = 80? So a formula where I could say:
900 is 90
400 is 80
233 is 70
150 is 60
etc.
I hope you understand my point.
Thanks in advance.
So you know $x=\frac {b-a}{a}\cdot 100$ but you want to know $y=\frac{b-a}{b}\cdot 100$. As $\frac{x}{100}+1=\frac{b}{a}$ and $y=\frac{x}{\frac{b}{a}}$ you get $y=\frac{x}{\frac{x}{100}+1}$.