-10% is the change from 320 to 288
Calculation steps:
[( 288 - 320 ) ÷ 320] x 100 = -10%
Formula
Percentage change = [(288 - 320) / 320] x 100
Subtract the new number by the original number
288 - 320 = -32
-32 ÷ 320 = -0.1
-0.1 x 100 = -10%
Example