Question

the diameter of a circle is 18 centimeters. what is the area?
give the exact answer in simplest form.
square centimeters

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 area formula

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

Answer:

\(81\pi\)