-95% is the change from 20 to 1
Calculation steps:
[( 1 - 20 ) ÷ 20] x 100 = -95%
Formula
Percentage change = [(1 - 20) / 20] x 100
Subtract the new number by the original number
1 - 20 = -19
-19 ÷ 20 = -0.95
-0.95 x 100 = -95%
Example