Question

If a circle has a circumference of 81 pi what is its radius and area?

Answer 1

Answer:

r = 40.5

A = 1640.25 pi

Step-by-step explanation:

The circumference is given by

C = pi *d

81 pi = pi *d

Divide each side by pi

81 = d

We can find the radius

d = 2r

81 = 2r

Divide each side by 2

81/2 = r

40.5

Now we can find the area

A = pi r^2

A = pi ( 40.5)^2

A =1640.25 pi

Answer 2

Answer:

Solution :-

$\sf Circumference = 2\pi r$

$\sf \: 81 \pi = 2\pi r$

$\sf \: 81 = 2r$

$\sf \dfrac{81}{2} = r$

$\sf \: 40.5 = r$

Area = πr²

$\sf \: Area = 3.14 \times 40.5 \times 40.5$

$\sf \: Area = 5150.38$

$\sf \: Area = 5150.38 \: units {}^{2}$