5. If the area of the circle is 81π units?, what is the circumference of the circle?

The circumference of the circle is 18π.

Step-by-step explanation:

First you have to acknowledge the equation on how to find the area of a circle. Which is A = πr².

Next you put 81π = πr².

Then you divide π from 81 to the other side and that should eliminate π from both sides.

Now you are left with 81 = r². Which if you square 81, it would become ±9. It would most likely be a positive 9.

So now you just add 9+9 to get the diameter because to get the circumference you need to know the equation to get it, which is diameter x π.

The full answer could be 18π or the simplified version which is estimated to the nearest hundredth which is 56.55.