Question

The area of a circle is 81π m². What is the circumference, in meters? Express your answer in terms of π.

Answer 1

18πm Hope this helps (: <3

Answer 2

`18\pi m`

Explanation:

to find the circumference we need to find the radius of the circle.

For this, we use the formula for the area :

`a=\pi r^2`

where
`a` is the area,
`\pi` is a constant
`\pi =3.1416` and
`r` is the radius.

we know that the area is:

`a=81\pi m^2`

so we substitue this into the previous formula:

`81\pi m^2=\pi r^2`

and we solve for
`r` :

`(81\pi m^2)/(\pi )=r^2\\ \\81m^2=r^2\\\\√(81m^2)=r\\\\9m=r`

the radius is 9 meters.

Now we use the formula for circumference of a circle:

`C=2 \pi r`

and substitute the value that we've just found for r:

`C=2\pi (9m)\\C=18\pi m`

the answer in terms of
`\pi` is
`18\pi` meters is the circumference