-66.09% is the change from 640 to 217
Calculation steps:
[( 217 - 640 ) ÷ 640] x 100 = -66.09%
Formula
Percentage change = [(217 - 640) / 640] x 100
Subtract the new number by the original number
217 - 640 = -423
-423 ÷ 640 = -0.6609375
-0.6609375 x 100 = -66.09%