-49.1% is the change from 668 to 340
Calculation steps:
[( 340 - 668 ) ÷ 668] x 100 = -49.1%
Formula
Percentage change = [(340 - 668) / 668] x 100
Subtract the new number by the original number
340 - 668 = -328
-328 ÷ 668 = -0.49101796407185627
-0.49101796407185627 x 100 = -49.1%