Question

a circle has an area of 81 3.14 units . what is the diameter in terms of 3.14a circle has an area of 81 Pi square units what is the diameter of the circle

Answer 1

18 units

Explanation:

`\pi r^2=81\pi`

Solve for
`r`:

`\pi r^2=81\pi \\r^2=81\\r=9`

Knowing diameter is 2*r, we can apply the formula to find diameter

`d=2*r\\d=2*9\\d=18`

Answer 2

You have posted 2 separate questions here. Please, next time, separate them with a blank line:

A circle has an area of 81 3.14 units . what is the diameter in terms of 3.14?

I'd prefer you write this as
"A circle has an area of 81 pi units . what is the diameter in terms of pi?

Area of a circle = A = pi*r^2. Note that r= diameter / 2. Here, the area is 81 pi square units, or 9^2 * pi square units, which means that the radius is 9 units. The diameter is then 2(9 units) = 18 units.


Your second question, separated from the first, is:

"a circle has an area of 81 Pi square units what is the diameter of the circle?"

Use the following formula or formulas: d = 2*r; A = pi*r^2; A = pi*(d/2)^2. Find r first, and then find d.