What is the area of a circle with a diameter of 18 inches?

To determine the area of a circle, you can use the formula A = πr², where A represents the area and r represents the radius of the circle.

First, if the diameter of the circle is 18 inches, the radius is half of that, which is 9 inches (since radius r = diameter / 2).

Next, substitute the radius into the area formula:

A = π(9)²

A = π(81)

A ≈ 3.14159 × 81

A ≈ 254.46 square inches.

This calculation gives us that the area of the circle with a diameter of 18 inches is approximately 254.46 square inches, making this the correct answer.

Knowing that this area is derived from substituting the radius into the area formula reinforces the understanding of how to calculate the area of circles using given measurements, particularly diameter.