102.5% is the change from 40 to 81
Calculation steps:
[( 81 - 40 ) ÷ 40] x 100 = 102.5%
Formula
Percentage change = [(81 - 40) / 40] x 100
Subtract the new number by the original number
81 - 40 = 41
41 ÷ 40 = 1.025
1.025 x 100 = 102.5%
Example