Surface Areas and Volumes — Maths STD 9 — Question

The amount of cloth required to make a tent is equal to the curved surface area of a cone.
$\text{l}=\sqrt{\text{r}^2+\text{h}^2}$
$\text{l}=\sqrt{7^2+24^2}$
$\text{l}=\sqrt{49+576}$
$\text{l}=25\text{m}$
Curved surface area of the cone $=\pi\text{rl}$
$=\frac{22}{7}\times7\times25$
$=550\text{m}^2$
Length of the cloth $=\frac{\text{area}}{\text{width}}$
$=\frac{550}{2.5}=220\text{m}$