Question

Find the area of a circle with the circumference 18(pi)

Answer 1

Circumference = $2\pi r$

$\frac{18\pi}{2\pi} = \frac{2\pi r }{2\pi }$

18 ÷ 2 = 9

r = 9

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Area = $\pi r^{2}$

= $\pi (9)^{2}$

= 81$\pi$ units².

Answer 2

Answer:

D 81 pi units^2

Step-by-step explanation:

The circumference of a circle  is given by

C = 2 * pi *r

18 pi = 2 * pi *r

Divide each side by 2 * pi

18 pi / (2 pi) = 2 pi * r/ (2 pi)

9 = r

Now we can find the area.  Area is given by

A = pi r^2

A = pi * 9^2

A = 81 pi units^2