303.03% is the change from 99 to 399
Calculation steps:
[( 399 - 99 ) ÷ 99] x 100 = 303.03%
Formula
Percentage change = [(399 - 99) / 99] x 100
Subtract the new number by the original number
399 - 99 = 300
300 ÷ 99 = 3.0303030303030303
3.0303030303030303 x 100 = 303.03%