Question

The diameter of a cone is $1.4cm$. Its slant height is $4.2cm$. Find curved surface area.

• A. $9.24{cm}^2$
• B. $2.24{cm}^2$
• C. $8.14{cm}^2$
• D. $6.94{cm}^2$

Answer 1

The correct option is A $9.24{cm}^2$

We know, the curved surface area of a right circular cone $=\pi rl$.

Given, diameter of the cone $=1.4cm$.

Then, radius $r=\frac{d}{2}=\frac{1.4}{2}=0.7cm$

Also, given slant height $l=4.2cm$.

Then, the curved surface area $=\pi \times 0.7\times 4.2$

$=\frac{22}{7}\times 0.7\times 4.2$ $=9.24{\text{cm}}^2$.

Therefore, option $A$ is the correct.