<h2><u><em>at x = 3 D = .1086</em></u></h2><h2><u><em /></u></h2><h2><u><em>at x = 4 D = .0869</em></u></h2><h2><u><em /></u></h2><h2><u><em>at x = 5 D = .0724</em></u></h2>
c = circumference
pi = 3.14
r = radius = 9 inches
d = diameter
c=pi*d
The radius is half of the diameter, d = 2r. Then d = 2*9=18.
plug into equation. c= pi*d = 3.14*18
round accordingly and you may want to include that the measurement you end up with is in inches.
