31.15% is the change from 642 to 842
Calculation steps:
[( 842 - 642 ) ÷ 642] x 100 = 31.15%
Formula
Percentage change = [(842 - 642) / 642] x 100
Subtract the new number by the original number
842 - 642 = 200
200 ÷ 642 = 0.3115264797507788
0.3115264797507788 x 100 = 31.15%