-55% is the change from 100 to 45
Calculation steps:
[( 45 - 100 ) ÷ 100] x 100 = -55%
Formula
Percentage change = [(45 - 100) / 100] x 100
Subtract the new number by the original number
45 - 100 = -55
-55 ÷ 100 = -0.55
-0.55 x 100 = -55%
Example