30% is the change from 640 to 832
Calculation steps:
[( 832 - 640 ) ÷ 640] x 100 = 30%
Formula
Percentage change = [(832 - 640) / 640] x 100
Subtract the new number by the original number
832 - 640 = 192
192 ÷ 640 = 0.3
0.3 x 100 = 30%
Example