171.84% is the change from 309 to 840
Calculation steps:
[( 840 - 309 ) ÷ 309] x 100 = 171.84%
Formula
Percentage change = [(840 - 309) / 309] x 100
Subtract the new number by the original number
840 - 309 = 531
531 ÷ 309 = 1.7184466019417475
1.7184466019417475 x 100 = 171.84%