Question

Find the surface area of the spheres of the following radii:

(1) r = 7 cm
(2) r = 10.5 cm
(3) r = 10 cm (π = 3.14)
(4) r = 2.8 cm
(5) r = 9.8 m
(6) r = 42 m

Answer 1

(1) Radius of sphere (r) = 7 cm
Surface area of sphere = 4πr²
$$\begin{gathered} =4\times \frac{22}{7}\times 7\times 7 \\ =616\mathrm{sq}\mathrm{cm} \end{gathered}$$

(2) Radius of sphere (r) = 10.5 cm
Surface area of sphere = 4πr²
$$\begin{gathered} =4\times \frac{22}{7}\times 10.5\times 10.5 \\ =1386\mathrm{sq}\mathrm{cm} \end{gathered}$$

(3) Radius of sphere (r) = 10 cm
Surface area of sphere = 4πr²
= 4 × 3.14 × 10 × 10
= 1256 sq cm

(4) Radius of sphere (r) = 2.8 cm
Surface area of sphere = 4πr²
$$\begin{gathered} =4\times \frac{22}{7}\times 2.8\times 2.8 \\ =98.56\mathrm{sq}\mathrm{cm} \end{gathered}$$

(5) Radius of sphere (r) = 9.8 m
Surface area of sphere = 4πr²
$$\begin{gathered} =4\times \frac{22}{7}\times 9.8\times 9.8 \\ =1207.36\mathrm{sq}\mathrm{m} \end{gathered}$$

(6) Radius of sphere (r) = 42 m
Surface area of sphere = 4πr²
$$\begin{gathered} =4\times \frac{22}{7}\times 42\times 42 \\ =22176\mathrm{sq}\mathrm{m} \end{gathered}$$