-84.5% is the change from 645 to 100
Calculation steps:
[( 100 - 645 ) ÷ 645] x 100 = -84.5%
Formula
Percentage change = [(100 - 645) / 645] x 100
Subtract the new number by the original number
100 - 645 = -545
-545 ÷ 645 = -0.8449612403100775
-0.8449612403100775 x 100 = -84.5%