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

i) Radius (r) of sphere = \(\frac{Diameter}{2} = \frac{14}{2} = 7 cm\)

Surface area of sphere
= \(4 {\pi} {r}^2\)
= [\(4 × \frac{22}{7} × (7)^2\) \({cm}^2\)]
= [\(4 × \frac{22}{7} × 7 × 7\) \({cm}^2\)]
= (88 × 7) \({cm}^2\)
= 616 \({cm}^2\)

Therefore, the surface area of a sphere having radius 14 cm is 616 \({cm}^2\).


ii) Radius (r) of sphere = \(\frac{Diameter}{2} = \frac{21}{2} = 10.5 cm\)

Surface area of sphere
= \(4 {\pi} {r}^2\)
= [\(4 × \frac{22}{7} × (10.5)^2\) \({cm}^2\)]
= [\(4 × \frac{22}{7} × 10.5 × 10.5\) \({cm}^2\)]
= (88 × 1.5 × 10.5) \({cm}^2\)
= 1386 \({cm}^2\)

Therefore, the surface area of a sphere having radius 10.5cm is 1386 \({cm}^2\).


iii) Radius (r) of sphere = \(\frac{Diameter}{2} = \frac{3.5}{2} = 1.75 cm\)

Surface area of sphere
= \(4 {\pi} {r}^2\)
= [\(4 × \frac{22}{7} × (1.75)^2\) \({m}^2\)]
= [\(4 × \frac{22}{7} × 1.75 × 1.75\) \({m}^2\)]
= ((88 × 1.75) \({m}^2\)
= 38.5 \({m}^2\)

Therefore, the surface area of a sphere having radius 3.5 m is 38.5 \({m}^2\).