-51% is the change from 100 to 49
Calculation steps:
[( 49 - 100 ) ÷ 100] x 100 = -51%
Formula
Percentage change = [(49 - 100) / 100] x 100
Subtract the new number by the original number
49 - 100 = -51
-51 ÷ 100 = -0.51
-0.51 x 100 = -51%
Example