2500% is the change from 15 to 390
Calculation steps:
[( 390 - 15 ) ÷ 15] x 100 = 2500%
Formula
Percentage change = [(390 - 15) / 15] x 100
Subtract the new number by the original number
390 - 15 = 375
375 ÷ 15 = 25
25 x 100 = 2500%
Example