Question

A cone has a base radius of 5cm and a height of 12cm.calculate (a) its slant height ( b) curved surface area

Answer 1

slant height of a cone =

$l = \sqrt{ {r}^{2} + {h}^{2} }$

$l = \sqrt{ {5}^{2} + {12}^{2} }$

$l = \sqrt{25 + 144}$

$l = \sqrt{169}$

$l = 13$

slant height = 13cms

curved surface area of acone =

$\pi {r}^{2} + \pi \: lr$

$= \pi {5}^{2} + \pi13 \times 5$

$= \pi25 + \pi65$