Question

The diameter of the base of a right circular cone is 21cm and its height is 20cm.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 $1914c{m}^2$


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