-50.93% is the change from 642 to 315
Calculation steps:
[( 315 - 642 ) ÷ 642] x 100 = -50.93%
Formula
Percentage change = [(315 - 642) / 642] x 100
Subtract the new number by the original number
315 - 642 = -327
-327 ÷ 642 = -0.5093457943925234
-0.5093457943925234 x 100 = -50.93%