Question:
Note Use $\pi=\frac{22}{7}$, unless stated otherwise.
The slant height and base diameter of a conical tomb are 25 m and 14 m respectively. Find the cost of whitewashing its curved surface at the rate of ₹ 12 per m2.
Solution:
Slant height of the conical tomb, l = 25 m
Radius of the conical tomb, $r=\frac{14}{2}=7 \mathrm{~m}$
$\therefore$ Curved surface area of the conical tomb $=\pi r l=\frac{22}{7} \times 7 \times 25=550 \mathrm{~m}^{2}$
Rate of whitewashing = ₹ 12 per m2
∴ Cost of whitewashing the conical tomb
= Curved surface area of the conical tomb × Rate of whitewashing
= 550 × 12
= ₹ 6,600
Thus, the cost of whitewashing the conical tomb is ₹ 6,600.