23.53% is the change from 340 to 420
Calculation steps:
[( 420 - 340 ) ÷ 340] x 100 = 23.53%
Formula
Percentage change = [(420 - 340) / 340] x 100
Subtract the new number by the original number
420 - 340 = 80
80 ÷ 340 = 0.23529411764705882
0.23529411764705882 x 100 = 23.53%