-34.53% is the change from 640 to 419
Calculation steps:
[( 419 - 640 ) ÷ 640] x 100 = -34.53%
Formula
Percentage change = [(419 - 640) / 640] x 100
Subtract the new number by the original number
419 - 640 = -221
-221 ÷ 640 = -0.3453125
-0.3453125 x 100 = -34.53%