Question

The radius of a cone is $3cm$ and vertical height is $4cm$. Then the area of the curved surface is:

• A. $41.14$ $c{m}^2$
• B. $42.14$ $c{m}^2$
• C. $43.14$ $c{m}^2$
• D. $47.14$ $c{m}^2$

Answer 1

The correct option is D $47.14$ $c{m}^2$

We have, $r=3cm$ and $h=4cm$.
Let $lcm$ be the slant height of the cone,

then $l^2=r^2+h^2$
$\Rightarrow l^2=3^2+4^2$
$\Rightarrow l=\sqrt{25}=5cm$.

$\therefore$ Area of the curved surface $=\pi rl$

$=(\frac{22}{7}\times 3\times 5)c{m}^2=47.14c{m}^2$.

Hence, option $D$ is correct.