-89.61% is the change from 491 to 51
Calculation steps:
[( 51 - 491 ) ÷ 491] x 100 = -89.61%
Formula
Percentage change = [(51 - 491) / 491] x 100
Subtract the new number by the original number
51 - 491 = -440
-440 ÷ 491 = -0.8961303462321792
-0.8961303462321792 x 100 = -89.61%