-4.18% is the change from 670 to 642
Calculation steps:
[( 642 - 670 ) ÷ 670] x 100 = -4.18%
Formula
Percentage change = [(642 - 670) / 670] x 100
Subtract the new number by the original number
642 - 670 = -28
-28 ÷ 670 = -0.041791044776119404
-0.041791044776119404 x 100 = -4.18%