-15.63% is the change from 320 to 270
Calculation steps:
[( 270 - 320 ) ÷ 320] x 100 = -15.63%
Formula
Percentage change = [(270 - 320) / 320] x 100
Subtract the new number by the original number
270 - 320 = -50
-50 ÷ 320 = -0.15625
-0.15625 x 100 = -15.63%