50% is the change from 20 to 30
Calculation steps:
[( 30 - 20 ) ÷ 20] x 100 = 50%
Formula
Percentage change = [(30 - 20) / 20] x 100
Subtract the new number by the original number
30 - 20 = 10
10 ÷ 20 = 0.5
0.5 x 100 = 50%
Example