The area, A of a circle is given by the formulae below:
[tex]A=\pi r^2=\frac{\pi d^2}{4}[/tex]
where:
A = area
r = radius = 0.5 x diameter = 0.5 x 20 = 10ft
d= diameter = 2ce the value of the radius = 20ft
This gives A to be
[tex]\begin{gathered} A=\pi\times10^2 \\ A=3.14\times100=314ft^2 \end{gathered}[/tex]
Area of the circle = 314 sq ft
