1900% is the change from 21 to 420
Calculation steps:
[( 420 - 21 ) ÷ 21] x 100 = 1900%
Formula
Percentage change = [(420 - 21) / 21] x 100
Subtract the new number by the original number
420 - 21 = 399
399 ÷ 21 = 19
19 x 100 = 1900%
Example