Question

The total area of sheet required to make an open cone of height $24cm$ and radius $7cm$ is:

• A. 470 $c{m}^2$
• B. 450 $c{m}^2$
• C. 425 $c{m}^2$
• D. 550 $c{m}^2$

Answer 1

Answer: (D)

The correct option is D 550 $c{m}^2$
Given, height of cone is $h=24cm$ and radius is $r=7cm$.

Then, area of sheet required = surface area of cone

$=\pi rl=\pi r\left(\sqrt{r^2+h^2}\right)=2\times \frac{22}{7}\times 7\left(\sqrt{(24{)}^2+(7{)}^2}\right)=2\times 22\times 25=550c{m}^2$.

Hence, option $D$ is correct.