Question:
The height of a cone is 24 cm and the diameter of its base is 14 cm. The curved surface area of the cone is
(a) 528 cm2
(b) 550 cm2
(c) 616 cm2
(d) 704 cm2
Solution:
(b) $550 \mathrm{~cm}^{2}$
$l=\sqrt{r^{2}+h^{2}}$
$=\sqrt{7^{2}+24^{2}}$
$=\sqrt{49+576}$
$=\sqrt{625}$
$=25 \mathrm{~cm}$
$\therefore$ Curved surface area of the cone $=\pi r l$
$=\frac{22}{7} \times 7 \times 25$
$=550 \mathrm{~cm}^{2}$