Question

What is the total surface area of a cone if its diameter =$1$ ft and slant height = $12$ ft. (use $\pi =3.14$).

• A. $11.625{ft}^2$
• B. $18.625{ft}^2$
• C. $19.625{ft}^2$
• D. $19.625ft$

Answer 1

Answer: (C)

$19.625{ft}^2$

Given, diameter, $d=1$ ft.

Then, radius $r=\frac{d}{2}=\frac{1}{2}$ ft.

Therefore, surface area of a cone $=\pi rs+\pi r^2$
$=3.14\times \frac{1}{2}\times 12+3.14\times \frac{1}{2}\times \frac{1}{2}$
$=18.84+0.785$
$=19.625{ft}^2$.

Hence, option $C$ is correct.