30.35% is the change from 491 to 640
Calculation steps:
[( 640 - 491 ) ÷ 491] x 100 = 30.35%
Formula
Percentage change = [(640 - 491) / 491] x 100
Subtract the new number by the original number
640 - 491 = 149
149 ÷ 491 = 0.3034623217922607
0.3034623217922607 x 100 = 30.35%