Pre-Algebra Examples

 $\begin{array}{r} r = & 9 m \end{array}$

Step 1

The circumference of a circle is equal to Pi $π$ times the diameter $d$ .

$π \cdot (d i a m e t e r)$

Step 2

Since the diameter $d$ is equal to $2$ times the radius $r$ , the formula for circumference using radius is $2 π r$ .

$2 π \cdot (r a d i u s)$

Step 3

Substitute the value of the radius $r = 9$ into the formula for the area of a circle. Pi $π$ is approximately equal to $3.14$ .

$2 \cdot π \cdot 9$

Step 4

Multiply $9$ by $2$ .

$18 π$ m