3.07% is the change from 815 to 840
Calculation steps:
[( 840 - 815 ) ÷ 815] x 100 = 3.07%
Formula
Percentage change = [(840 - 815) / 815] x 100
Subtract the new number by the original number
840 - 815 = 25
25 ÷ 815 = 0.03067484662576687
0.03067484662576687 x 100 = 3.07%