Question

the diameter of a circle is 18 cm. find its area in terms of π.

Explanation:

Step1: Find the radius

The radius \(r\) of a circle is half of the diameter \(d\). Given \(d = 18\) cm, so \(r=\frac{d}{2}=\frac{18}{2}=9\) cm.

Step2: Use the formula for the area of a circle

The formula for the area of a circle is \(A=\pi r^{2}\). Substitute \(r = 9\) into the formula: \(A=\pi\times(9)^{2}\).
Since \(9^{2}=81\), then \(A = 81\pi\) \(cm^{2}\).

Answer:

The area of the circle is \(81\pi\) \(cm^{2}\).