Question

Find the circumference and area of the circle if the diameter is $77cm.$

Answer 1

Step 1 Finding the circumference of the circle:

Circumference of the circle=$2\mathrm{\pi r},\mathrm{where}\mathrm{r}\mathrm{is}\mathrm{the}\mathrm{radius}\mathrm{of}\mathrm{the}\mathrm{circle}.$

$$\begin{gathered} =2\times \frac{22}{7}\times \frac{77}{2}(Sincediameter=77cmandradius=\frac{77}{2}) \\ =2\times 11\times 11 \\ =242cm. \end{gathered}$$

Hence, the circumference of the circle is $242cm.$

Step 2 Finding the area of the circle:

Area of the circle = ${\mathrm{\pi r}}^2,\mathrm{where}\mathrm{r}\mathrm{is}\mathrm{the}\mathrm{radius}\mathrm{of}\mathrm{the}\mathrm{circle}.$

$$\begin{gathered} =\frac{22}{7}\times \frac{77}{2}\times \frac{77}{2} \\ =\frac{9317}{2} \\ =4658.5c{m}^2. \end{gathered}$$

Hence, the area of the circle is $4658.5c{m}^2$