3900% is the change from 8 to 320
Calculation steps:
[( 320 - 8 ) ÷ 8] x 100 = 3900%
Formula
Percentage change = [(320 - 8) / 8] x 100
Subtract the new number by the original number
320 - 8 = 312
312 ÷ 8 = 39
39 x 100 = 3900%
Example