50% is the change from 340 to 510
Calculation steps:
[( 510 - 340 ) ÷ 340] x 100 = 50%
Formula
Percentage change = [(510 - 340) / 340] x 100
Subtract the new number by the original number
510 - 340 = 170
170 ÷ 340 = 0.5
0.5 x 100 = 50%
Example