300% is the change from 70 to 280
Calculation steps:
[( 280 - 70 ) ÷ 70] x 100 = 300%
Formula
Percentage change = [(280 - 70) / 70] x 100
Subtract the new number by the original number
280 - 70 = 210
210 ÷ 70 = 3
3 x 100 = 300%
Example