Question

The radii of the circular ends of a solid frustum of a cone are 33 cm and 27 cm and its slant height is 10 cm. Find its total surface area. [Use $\mathrm{\pi }=3.14.]$

Answer 1

Greater radius = R = 33 cm
Smaller radius = r = 27 cm
Slant height = l = 10 cm

Surface area of the frustum

$$\begin{gathered} =\mathrm{\pi }{R}^2+\mathrm{\pi }{r}^2+\mathrm{\pi }l\left(R+r\right) \\ =\mathrm{\pi }\left[R^2+r^2+l\left(R+r\right)\right] \\ =\left[{33}^2+{27}^2+10\left(33+27\right)\right]\mathrm{\pi } \\ =\left[1089+729+10\left(60\right)\right]\mathrm{\pi } \\ =2418\times 3.14 \\ =7592.52{\mathrm{cm}}^2 \end{gathered}$$