Question:
The dome of a building is in the form of a hemisphere. Its radius is 63dm. Find the cost of painting it at the rate of Rs.2 per sq m.
Solution:
Dome radius = 63 dm = 6.3 m
Inner surface area of dome $=2 \pi r^{2}$
$=2 \times 3.14 \times(6.3)^{2}$
$=249.48 \mathrm{~m}^{2}$
Now, cost of $1 \mathrm{~m}^{2}=$ Rs. 2
Therefore cost of $249.48 \mathrm{~m}^{2}=$ Rs. $(249.48 \times 2)=$ Rs. $498.96$
