-3.57% is the change from 280 to 270
Calculation steps:
[( 270 - 280 ) ÷ 280] x 100 = -3.57%
Formula
Percentage change = [(270 - 280) / 280] x 100
Subtract the new number by the original number
270 - 280 = -10
-10 ÷ 280 = -0.03571428571428571
-0.03571428571428571 x 100 = -3.57%