Question

The radius of a circle is $21cm$. Find its circumference $(\text{Take}\pi =3\frac{1}{7})$.

Answer 1

Radius of circle $=21cm$.

Circumference of circle $=2\pi r$

$=2\times \frac{22}{7}\times 21(\because \pi =\frac{22}{7})$

$=2\times 22\times 3$

$\therefore$ Circumference of circle $=132cm$.