A circus tent is cylindrical to a height of 4 m and conical above it.
Question:

A circus tent is cylindrical to a height of 4 m and conical above it. If its diameter is 105 m and its slant height is 40 m, the total area of canvas required is
(a) 1760 m2
(b) 2640 m2
(c) 3960 m2
(d) 7920 m2

Solution:

(d) 7920 m2
Total area of the canvas required = (Curved surface area of the cylinder) + (Curved surface area of the cone)

$=(2 \pi r h+\pi r l)$

$=\left(2 \times \frac{22}{7} \times \frac{105}{2} \times 4\right)+\left(\frac{22}{7} \times \frac{105}{2} \times 40\right)\left[d=105 \mathrm{~cm} \Rightarrow r=\frac{105}{2} \mathrm{~cm}\right]$

$=(1320+6600) \mathrm{m}^{2}$

$=7920 \mathrm{~m}^{2}$