Question

A joker's cap is in the form of a right circular cone of base radius $7cm$ and height $24cm$. Find the areas of the sheet required to make $10$ such caps.

• A. $5000c{m}^2$
• B. $6200c{m}^2$
• C. $5500c{m}^2$
• D. $6000c{m}^2$

Answer 1

The correct option is C $5500c{m}^2$

We know, the curved surface area of cone (hollow at bottom) $=\pi r\ell$

Slant height, $\ell =\sqrt{{24}^2+7^2}=25cm$.

Then, $A=\pi \times 7\times 25$

$=\frac{22}{7}\times 7\times 25$

$=22\times 25$

$=550c{m}^2$.

$\therefore$ For $10$ caps, the area of sheet required is $=10\times 550c{m}^2=5500c{m}^2$.

Hence, option $C$ is correct.