12.35% is the change from 81 to 91
Calculation steps:
[( 91 - 81 ) ÷ 81] x 100 = 12.35%
Formula
Percentage change = [(91 - 81) / 81] x 100
Subtract the new number by the original number
91 - 81 = 10
10 ÷ 81 = 0.12345679012345678
0.12345679012345678 x 100 = 12.35%