Question

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

Answer 1

Circumference =
`2\pi r`

`(18\pi)/(2\pi) = (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

D 81 pi units^2

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