Question

1. what is the area of a circle with a diameter of 18 cm? 1296π cm² 324π cm² 18π cm² 81π cm²

Explanation:

Step1: Find the radius

The diameter \( d = 18\) cm, and the radius \( r=\frac{d}{2}\). So \( r=\frac{18}{2}=9\) cm.

Step2: Calculate the area

The formula for the area of a circle is \( A = \pi r^{2}\). Substitute \( r = 9\) into the formula: \( A=\pi\times9^{2}=\pi\times81 = 81\pi\) \( cm^{2}\).

Answer:

\( 81\pi\space cm^{2}\) (the option corresponding to this answer, e.g., if it's the fourth option, write: D. \( 81\pi\space cm^{2}\))