Question

Find the surface area of a sphere of diameter:
(i) 14 cm
(ii) 21 cm
(iii) 3.5 m

Answer 1

(i) Diameter, d = 14 cm
Radius, r = $\frac{14cm}{2}$ = 7cm

Surface area of a sphere = $4\pi r^2$
= 4 × $\frac{22}{7}$ × 7cm × 7cm
= 616 cm2

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(ii) Diameter, d = 21 cm
Radius, r = $\frac{21cm}{2}$

Surface area of a sphere = $4\pi r^2$
$= \frac{4}{2} × \frac{22}{7} × \frac{21}{2} × \frac{21}{2}$
= 1386 cm2

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(iii) Diameter, d = 3.5 m
Radius, r =$\frac{3.5}{2}$ = 1.75m

Surface area of a sphere = $4\pi r^2$
= 4 × $\frac{22}{7}$× 1.75m x 1.75m
= 38.5 m2

The surface area of a sphere with diameters 14 cm, 21 cm, and 3.5 m are 616 cm2, 1386 cm2, and 38.5 m2 respectively.