The formula for the area of a circle is A: [tex] \pi [/tex]r²
If you plug in the numbers, you get 81[tex] \pi [/tex]: [tex] \pi [/tex](x)²
If you divide the [tex] \pi [/tex] on either side, they cancel each other out, leaving 81: (x)²
You will find the square root of 81, which is 9.
Your radius is then 9.
The circumference formula is C: 2[tex] \pi [/tex]r
If you plug the numbers in, you get C: 2[tex] \pi [/tex](9)
You do the math and get the circumference, C: 18[tex] \pi [/tex] units²
Hope this helped!
