61.1% is the change from 509 to 820
Calculation steps:
[( 820 - 509 ) ÷ 509] x 100 = 61.1%
Formula
Percentage change = [(820 - 509) / 509] x 100
Subtract the new number by the original number
820 - 509 = 311
311 ÷ 509 = 0.6110019646365422
0.6110019646365422 x 100 = 61.1%