12.5% is the change from 40 to 45
Calculation steps:
[( 45 - 40 ) ÷ 40] x 100 = 12.5%
Formula
Percentage change = [(45 - 40) / 40] x 100
Subtract the new number by the original number
45 - 40 = 5
5 ÷ 40 = 0.125
0.125 x 100 = 12.5%
Example