-51.79% is the change from 840 to 405
Calculation steps:
[( 405 - 840 ) ÷ 840] x 100 = -51.79%
Formula
Percentage change = [(405 - 840) / 840] x 100
Subtract the new number by the original number
405 - 840 = -435
-435 ÷ 840 = -0.5178571428571429
-0.5178571428571429 x 100 = -51.79%