what is an equation for finding %

x / 100 = part / whole

If your part is let's say 20 and the whole is 40 you need to find the percent right?

x / 100 = 20 / 40

40 / 40 x = 400 / 40

0 10

the percentage is not 10 it is 50%

x / 100 =part / whole

x / 100 = 0.5

Cross multiply

x =100 x 0.5 =50% - what you want.