-91.18% is the change from 340 to 30
Calculation steps:
[( 30 - 340 ) ÷ 340] x 100 = -91.18%
Formula
Percentage change = [(30 - 340) / 340] x 100
Subtract the new number by the original number
30 - 340 = -310
-310 ÷ 340 = -0.9117647058823529
-0.9117647058823529 x 100 = -91.18%