2.5% is the change from 40 to 41
Calculation steps:
[( 41 - 40 ) ÷ 40] x 100 = 2.5%
Formula
Percentage change = [(41 - 40) / 40] x 100
Subtract the new number by the original number
41 - 40 = 1
1 ÷ 40 = 0.025
0.025 x 100 = 2.5%
Example