A 5-m-wide cloth is used to make a conical tent of base diameter 14 m and height 24 m. Find the cost of cloth used, at the rate of ₹25 per metre.
We have,
Width of the cloth, $B=5 \mathrm{~m}$,
Radius of the conical tent, $r=\frac{14}{2}=7 \mathrm{~m}$ and
Height of the conical tent, $h=24 \mathrm{~m}$
Let the length of the cloth used for making the tent be $L$.
Also,
The slant height of the conical tent, $l=\sqrt{r^{2}+h^{2}}$
$=\sqrt{7^{2}+24^{2}}$
$=\sqrt{49+576}$
$=\sqrt{625}$
$=25 \mathrm{~m}$
Now,
The curved surface of the conical tent $=\pi r l$
$=\frac{22}{7} \times 7 \times 25$
$\Rightarrow$ The area of the cloth used for making the tent $=550 \mathrm{~m}^{2}$
$\Rightarrow L B=550$
$\Rightarrow L=\frac{550}{B}$
$\Rightarrow L=\frac{550}{5}$
$\Rightarrow L=110 \mathrm{~m}$
So, the cost of the cloth used $=25 \times 110=₹ 2750$
So, the cost of the cloth used for making the tent is ₹2750.