-50% is the change from 220 to 110
Calculation steps:
[( 110 - 220 ) ÷ 220] x 100 = -50%
Formula
Percentage change = [(110 - 220) / 220] x 100
Subtract the new number by the original number
110 - 220 = -110
-110 ÷ 220 = -0.5
-0.5 x 100 = -50%
Example