please help its math

Let the length of the radius = r feet.
Diameter = 2r = 2 x 6.8 = 13.6 feet
Circumference = 2[tex]\pi[/tex]r = 2 x 3.14 x 6.8 = 42.704 feet = approx. 42.7 feet
The diameter is 13.60 feet.
The circumstance is approximately 42.70 feet.
Look at the attached picture
Hope it will help you