-49.25% is the change from 670 to 340
Calculation steps:
[( 340 - 670 ) ÷ 670] x 100 = -49.25%
Formula
Percentage change = [(340 - 670) / 670] x 100
Subtract the new number by the original number
340 - 670 = -330
-330 ÷ 670 = -0.4925373134328358
-0.4925373134328358 x 100 = -49.25%