Lateral surface area of frustum of cone = $\pi (r_1+r_2)l$

Q. Lateral surface area of frustum of cone = $\pi (r_1+r_2)l$

Q. Question 7
The curved surface area of a frustum of a cone is $\pi (r_1+r_2)l$, where $l=\sqrt{h^2+(r_1+r_2{)}^2}$ $r_{1}and{r}_2$ are the radii of the two ends of the frustum and h is the vertical height.

Q. Lateral surface area of the frustum of a cone is

Q. The circumferences of circular faces of a frustum are 132 cm and 88 cm and its height is 24 cm. To find the curved surface area of the frustum complete the following activity.($\mathrm{\pi }=\frac{22}{7}$)

circumference₁ = 2$\mathrm{\pi }$r₁ = 132

r₁ = $\frac{132}{\mathrm{\pi }}=\boxed{134}$

circumference₂ =2$\mathrm{\pi }$r₂= 88

r₂= $\frac{88}{2\mathrm{\pi }}=\boxed{134}$

slant height of frustum, l = $$\begin{gathered} \sqrt{h^2+{\left(r_1-r_2\right)}^2} \\ \sqrt{{\boxed{1223}}^2+\boxed{1234}{}^2} \\ =\boxed{1234}\mathrm{cm} \end{gathered}$$

curved surface area of the frustum = $\mathrm{\pi }$ (r₁ + r₂ ) l

= $$\begin{gathered} \mathrm{\pi }\times \boxed{123}\times \boxed{132} \\ =\boxed{123}\mathrm{sq}.\mathrm{cm}. \end{gathered}$$

Q. What is the formula for the lateral surface area of the given frustum:

Where,
$R_1$ = radius of the base
$L$ = length of lateral side of the bigger cone of which the frustum is a part
$R_2$ = radius of the top surface
$l$ = length of lateral height of cone - lateral height the frustum (s)