Question

How do you find the circumference and area of a circle with diameter of 18 inches?

Answer 1

Circumference = `18pi` (56.52 inches) and area = `81pi` (254.34 inches)

Explanation:

We use the following formulas: `C = 2pir` and `A = pir^2`, where `C` is circumference, `A` is area, and `r` is the radius (half the diameter).

First step is finding the radius. As I mentioned above, the radius is half the diameter, or in this case, half of 18. So, our radius is 9 inches. Now we can apply our formulas; we'll start with circumference:

`C = 2pir`
`C = 2pi*9`
`C = 18pi`, or approximately 56.52 inches (remember that `pi ~= 3.14`)

For area:

`A = pir^2`
`A = pi*(9)^2`
`A = 81pi`, or approximately 254.34 inches