The area of a 10-inch circle is 78.54 square inches. Using the formula A = 1/4πd 2 where d is the diameter, we have Area = 1/4πd 2 = 1/4 x 3.14 x 10 2 = 78.54 What is the radius of a circle with a 10-inch diameter? The radius of a 10-inch circle is 5 inches because the radius is half of the diameter of a circle.
