Question

The formula used for surface area of cone is ($s$ denotes slant height):

• A. $\pi r(r+s)$ sq.units
• B. $\pi r(2r+s)$ sq.units
• C. $2\pi r(r+s)$ sq.units
• D. $\pi r{(r+s)}^2$ sq.units

Answer 1

The correct option is A $\pi r(r+s)$ sq.units

Since, surface area of cone $=$ Area of sector $+$ Area of circle

$=\pi rs+\pi r^2$ $=\pi r(r+s)$.

Therefore, surface area of a cone $=$ $\pi r(r+s)$ sq.units.

Hence, option $A$ is correct.