-57.14% is the change from 70 to 30
Calculation steps:
[( 30 - 70 ) ÷ 70] x 100 = -57.14%
Formula
Percentage change = [(30 - 70) / 70] x 100
Subtract the new number by the original number
30 - 70 = -40
-40 ÷ 70 = -0.5714285714285714
-0.5714285714285714 x 100 = -57.14%