83900% is the change from 1 to 840
Calculation steps:
[( 840 - 1 ) ÷ 1] x 100 = 83900%
Formula
Percentage change = [(840 - 1) / 1] x 100
Subtract the new number by the original number
840 - 1 = 839
839 ÷ 1 = 839
839 x 100 = 83900%
Example