Question

Find the total surface area of a cone, if its slant height is $9m$ and the radius of its base is $12m$.

• A. $792m^2$
• B. $452m^2$
• C. $682m^2$
• D. $987m^2$

Answer 1

The correct option is A $792m^2$

Given, radius of base of the cone$=12cm$
and slant height of the cone$=9cm$.

Then, total surface area of the cone$=\pi rl+\pi r^2=\pi r(l+r)$

$=\frac{22}{7}\times 12(9+12)$

$=\frac{22}{7}\times 12\times 21$

$=792m^2$.

Hence, option $A$ is correct.