Question

The circumference of a circle is 18pi ft. what is the area in square feet.

Answer 1

We have first the formula of the circumference of a circle

`C=2\pi r`

In order to know the area we need to know the radius of the circle, it can be obtained using the formula above and the next information.

C=18pi

r is the radius

`18\pi=2\pi r`

then we isolate the r

`\begin{gathered} r=(18\pi)/(2\pi) \\ r=9 \end{gathered}`

the radius is 9 ft

then we can calculate the area using the next formula

`A=\pi r^2`

we substitute the value of the radius

`\begin{gathered} A=\pi(9)^2 \\ A=81\pi ft^2 \\ A=254.47ft^2 \end{gathered}`