Premium Online Home Tutors
3 Tutor System
Starting just at 265/hour

# Find the surface area of a sphere of diameter:i) 14 cmii) 21 cmiii) 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 $${m}^2$$.