30% is the change from 70 to 91
Calculation steps:
[( 91 - 70 ) ÷ 70] x 100 = 30%
Formula
Percentage change = [(91 - 70) / 70] x 100
Subtract the new number by the original number
91 - 70 = 21
21 ÷ 70 = 0.3
0.3 x 100 = 30%
Example