29.85 inches
The circumference of a circle, with a diameter of 12 inches, is 37.7 inches.
15 x 3.1416, call it 47 and an eighth inches.
Area of a circle = pi*radius2 inches
12 inches
Area of circle in square inches = pi*radius squared
C = 131.95 inches.
3.141 square inches
The circumference is approx 4.71 feet.
21 feet = 21*12 inches = 252 inches - whether in a straight line or a circle or whatever.
A 1.25-inch diameter circle contains 1.227 square inches.
A circle with an 8-inch diameter has a perimeter of 25.1 inches.