-45% is the change from 20 to 11
Calculation steps:
[( 11 - 20 ) ÷ 20] x 100 = -45%
Formula
Percentage change = [(11 - 20) / 20] x 100
Subtract the new number by the original number
11 - 20 = -9
-9 ÷ 20 = -0.45
-0.45 x 100 = -45%
Example