Question

A tent is of the shape of a right circular cylinder upto height of $3$ metres and then becomes a right circular cone with maximum height of $13.5$ metres above the ground. Calculate the cost of painting the inner side of the tent at the rate of Rs.$2$ per square metre, if the radius of the base is $14$ metres.

• A. Rs.$2068$
• B. Rs.$1988$
• C. Rs.$1268$
• D. Rs.$2248$

Answer 1

The correct option is A Rs.$2068$

Radius of base of cylindrical portion$=14m$

Height of cylindrical portion$=3m$

Curved surface area of cylindrical part$=2\times \frac{22}{7}\times 14\times 3$

Height of conical part$=13.5-3=10.5m$

For conical part:$r=14m,h=10.5m$

$l=\sqrt{{\left(14\right)}^2+{\left(10.5\right)}^2}=\sqrt{306.25}$

$l=17.5m$

CSA of conical part$=\pi rl=\frac{22}{7}\times 14\times 17.5=770㎡$

$\therefore$Total area to be painted$=(264+770)㎡=1034㎡$

Cost of painting=Rs. $(1034\times 2)=$Rs. $2068$