-97.66% is the change from 642 to 15
Calculation steps:
[( 15 - 642 ) ÷ 642] x 100 = -97.66%
Formula
Percentage change = [(15 - 642) / 642] x 100
Subtract the new number by the original number
15 - 642 = -627
-627 ÷ 642 = -0.9766355140186916
-0.9766355140186916 x 100 = -97.66%