Find the surface area of a sphere of diameter
(i) $ 14 \mathrm{~cm} $
(ii) $ 21 \mathrm{~cm} $
(iii) $ 3.5 \mathrm{~m} $.

To do:

We have to find the surface area of the given spheres.

Solution:

(i) Diameter of the sphere $= 14\ cm$

This implies,

Radius of the sphere $(r) = \frac{14}{2}$

$= 7\ cm$

Therefore,

Surface area of the sphere $=4 \pi r^{2}$

$=4 \times \frac{22}{7} \times 7 \times 7$

$=616 \mathrm{~cm}^{2}$

(ii) Diameter of the sphere $=21 \mathrm{~cm}$

This implies,

Radius of the sphere $(r)=\frac{21}{2} \mathrm{~cm}$

Therefore,

Surface area of the sphere $=4 \pi r^{2}$

$=4 \times \frac{22}{7} \times \frac{21}{2} \times \frac{21}{2}$

$=1386 \mathrm{~cm}^{2}$

(iii) Diameter of the sphere $=3.5 \mathrm{~cm}$

This implies,

Radius of the sphere $(r)=\frac{3.5}{2}$

$=\frac{7}{2 \times 2}$

$=\frac{7}{4} \mathrm{~cm}$

Therefore,

Surface area of the sphere $=4 \pi r^{2}$

$=4 \times \frac{22}{7} \times \frac{7}{4} \times \frac{7}{4}$

$=\frac{77}{2}$

$=38.5 \mathrm{~cm}^{2}$

Tutorialspoint

Simply Easy Learning

Updated on: 10-Oct-2022

47 Views

Kickstart Your Career

Get certified by completing the course

Get Started