Question

Find the volume and surface area of a sphere whose radius is:
(i) 3.5 cm
(ii) 4.2 cm
(iii) 5 m

Answer 1

(i) Radius of the sphere = 3.5 cm
Now, volume = $\frac{4}{3}\mathrm{\pi }{r}^3$
$$\begin{gathered} =\frac{4}{3}\times \frac{22}{7}\times 3.5\times 3.5\times 3.5 \\ =179.67{\mathrm{cm}}^3 \end{gathered}$$

∴ Surface area = $4\mathrm{\pi }{r}^2$
$$\begin{gathered} =4\times \frac{22}{7}\times 3.5\times 3.5 \\ =154{\mathrm{cm}}^2 \end{gathered}$$

(ii) Radius of the sphere=4.2 cm
Now, volume = $\frac{4}{3}\mathrm{\pi }{r}^3$
$$\begin{gathered} =\frac{4}{3}\times \frac{22}{7}\times 4.2\times 4.2\times 4.2 \\ =310.46{\mathrm{cm}}^3 \end{gathered}$$

∴ Surface area = $4\mathrm{\pi }{r}^2$
$$\begin{gathered} =4\times \frac{22}{7}\times 4.2\times 4.2 \\ =221.76{\mathrm{cm}}^2 \end{gathered}$$

(iii) Radius of sphere=5 m
Now, volume = $\frac{4}{3}\mathrm{\pi }{r}^3$
=$$\begin{gathered} \frac{4}{3}\times \frac{22}{7}\times 5^3 \\ =523.81{\mathrm{cm}}^3 \end{gathered}$$

∴ Surface area = $4\mathrm{\pi }{r}^2$
$$\begin{gathered} =4\times \frac{22}{7}\times 5^2 \\ =314.29{\mathrm{cm}}^2 \end{gathered}$$