31.46% is the change from 639 to 840
Calculation steps:
[( 840 - 639 ) ÷ 639] x 100 = 31.46%
Formula
Percentage change = [(840 - 639) / 639] x 100
Subtract the new number by the original number
840 - 639 = 201
201 ÷ 639 = 0.3145539906103286
0.3145539906103286 x 100 = 31.46%