42.19% is the change from 64 to 91
Calculation steps:
[( 91 - 64 ) ÷ 64] x 100 = 42.19%
Formula
Percentage change = [(91 - 64) / 64] x 100
Subtract the new number by the original number
91 - 64 = 27
27 ÷ 64 = 0.421875
0.421875 x 100 = 42.19%
Example