Question

Note Use $\mathrm{\pi }=\frac{22}{7}$, unless stated otherwise.
A joker's cap is in the form of a right circular cone of base radius 7 cm and height 24 cm. Find the area of the sheet required to make 10 such caps.

Answer 1

Radius of the cone, r = 7 cm

Height of the cone, h = 24 cm

∴ Slant height of the cone, $l=\sqrt{r^2+h^2}=\sqrt{7^2+{24}^2}=\sqrt{49+576}=\sqrt{625}$ = 25 cm

Area of the sheet required to make one cap = Curved surface area of the cone = $\mathrm{\pi }rl=\frac{22}{7}\times 7\times 25$ = 550 cm²

∴ Area of the sheet required to make 10 such caps = 550 × 10 = 5500 cm²

Thus, the area of the sheet required to make 10 such jocker caps is 5500 cm².