Find the Circumference circle (2km)

 $\begin{array}{r} r = & 2 km \end{array}$

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

$π \cdot (d i a m e t e r)$

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

$2 π \cdot (r a d i u s)$

Substitute the value of the radius $r = 2$ into the formula for the area of a circle. Pi $π$ is approximately equal to $3.14$ .

$2 \cdot π \cdot 2$

Multiply $2$ by $2$ .

$4 π$ km

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