Question

The diameter of the base of a right circular cone is 42 cm and its height is 20 cm. Find the curved surface area of the cone.

• A. $3300c{m}^2$
• B. $1914c{m}^2$
• C. $1386c{m}^2$
• D. $26720c{m}^2$

Answer 1

The correct option is B $1914c{m}^2$

Given, diameter of the cone = 42 cm
$\Rightarrow$ Radius of the base of the cone = 21 cm


Slant height of the cone,
l =$\sqrt{h^2+r^2}$
= $\sqrt{{21}^2+{20}^2}$
= $29cm$
Curved surface area of cone
= $\pi rl$
= $\frac{22}{7}\times 21\times 29$
= $1914c{m}^2$