-50% is the change from 110 to 55
Calculation steps:
[( 55 - 110 ) ÷ 110] x 100 = -50%
Formula
Percentage change = [(55 - 110) / 110] x 100
Subtract the new number by the original number
55 - 110 = -55
-55 ÷ 110 = -0.5
-0.5 x 100 = -50%
Example