250% is the change from 120 to 420
Calculation steps:
[( 420 - 120 ) ÷ 120] x 100 = 250%
Formula
Percentage change = [(420 - 120) / 120] x 100
Subtract the new number by the original number
420 - 120 = 300
300 ÷ 120 = 2.5
2.5 x 100 = 250%
Example