30.09% is the change from 638 to 830
Calculation steps:
[( 830 - 638 ) ÷ 638] x 100 = 30.09%
Formula
Percentage change = [(830 - 638) / 638] x 100
Subtract the new number by the original number
830 - 638 = 192
192 ÷ 638 = 0.30094043887147337
0.30094043887147337 x 100 = 30.09%