69.23% is the change from 390 to 660
Calculation steps:
[( 660 - 390 ) ÷ 390] x 100 = 69.23%
Formula
Percentage change = [(660 - 390) / 390] x 100
Subtract the new number by the original number
660 - 390 = 270
270 ÷ 390 = 0.6923076923076923
0.6923076923076923 x 100 = 69.23%