Find the surface area of a sphere of diameter:

Solution:

(i) Given Diameter = 14 cm

Radius = Diameter/2

= 14/2 = 7 cm

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

$=4 \times 22 / 7 \times(7)^{2}$

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

(ii) Given Diameter = 21cm

Radius = Diameter/2

= 21/2 = 10.5 cm

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

$=4 \times 22 / 7 \times(10.5)^{2}$

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

(iii) Given diameter = 3.5 cm

Radius = Diameter/2

= 3.5/2 = 1.75 cm

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

$=4 \times 22 / 7 \times(1.75)^{2}$

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