Question

The slant height of a right circular cone is $10\text{m}$ and its height is $8\text{m}$. Find the area of its curved surface.

• A. $30\pi {\text{m}}^2$
• B. $40\pi {\text{m}}^2$
• C. $60\pi {\text{m}}^2$
• D. $80\pi {\text{m}}^2$

Answer 1

Answer: (C)

$60\pi {\text{m}}^2$

Curved Surface Area of cone = $\pi rl$

Slant height, $l=10\text{m}$

Height, $h=8\text{m}$

Radius, $r=\sqrt{l^2-h^2}$

$r=\sqrt{100-64}\text{m}$

$=6\text{m}$

CSA $=\pi \times 6\times 10{\text{m}}^2$

$=60\pi {\text{m}}^2$