Question

Find the circumference of the circle with a radius of $21cm$ by taking $\pi =\raisebox{1ex}{$22$}\!\left/ \!\raisebox{-1ex}{$7$}\right.$.

Answer 1

Find the circumference of the circle

Given that the radius of the circle is $21cm$

We know that if $r$ is the radius of the circle and $C$ the circumference of a circle then

Circumference of the circle $C=2\pi r$

$r=21cm$

$$\begin{gathered} C=2\pi r \\ \Rightarrow C=2\times \frac{22}{7}\times 21 \\ \Rightarrow C=2\times 22\times 3 \\ \Rightarrow C=132 \end{gathered}$$

Hence, the circumference of the circle is $132cm$.