Find the circumference and area of a circle of radius 4.2 cm.

We know that the circumference $C$ and area $A$ of a circle of radius $r$ are given by $C=2 \pi r$ and $A=\pi r^{2}$ respectively.

Here, $r=4.2 \mathrm{~cm}$

So substituting the value of r in above formulas,

Circumference of the circle

$C=2 \times \pi \times 4.2 \mathrm{~cm}$

$=2 \times \frac{22}{7} \times 4.2 \mathrm{~cm}$

$=26.4 \mathrm{~cm}$

Area of the circle

$A=\pi \times 4.2 \times 4.2 \mathrm{~cm}^{2}$

$=\frac{22}{7} \times 4.2 \times 4.2 \mathrm{~cm}^{2}$

$=55.4 \mathrm{~cm}^{2}$