-50% is the change from 70 to 35
Calculation steps:
[( 35 - 70 ) ÷ 70] x 100 = -50%
Formula
Percentage change = [(35 - 70) / 70] x 100
Subtract the new number by the original number
35 - 70 = -35
-35 ÷ 70 = -0.5
-0.5 x 100 = -50%
Example