99.5% is the change from 400 to 798
Calculation steps:
[( 798 - 400 ) ÷ 400] x 100 = 99.5%
Formula
Percentage change = [(798 - 400) / 400] x 100
Subtract the new number by the original number
798 - 400 = 398
398 ÷ 400 = 0.995
0.995 x 100 = 99.5%
Example