-90% is the change from 340 to 34
Calculation steps:
[( 34 - 340 ) ÷ 340] x 100 = -90%
Formula
Percentage change = [(34 - 340) / 340] x 100
Subtract the new number by the original number
34 - 340 = -306
-306 ÷ 340 = -0.9
-0.9 x 100 = -90%
Example