The radius of the base of a cone is 5 cm and its height is 12 cm. Its curved surface area is

(b) 65π cm2
Given: r = 5 cm, h = 12 cm

Slant height of the cone, $l=\sqrt{r^{2}+h^{2}}$

$=\sqrt{(5)^{2}+(12)^{2}}$

$=\sqrt{25+144}$

$=\sqrt{169}$

$=13 \mathrm{~cm}$

Hence, the curved surface area of the cone $=\pi r l$

$=(\pi \times 5 \times 13) \mathrm{cm}^{2}$

$=65 \pi \mathrm{cm}^{2}$