A frustum of a right circular cone is of height 16 cm with radii of its circular ends as 8 cm and 20 cm then what is its slant height? 

Given that,

A frustum of a right circular cone is of height

16 cm with radii of its ends as 8 cm and 20 cm.

Now we have to find the slant height $l$ of the cone.  

From the figure,  

Height of the cone h=16 cm

Radii of ends R=20 cm & r =8 cm

Let, radius of frustum cone be $d= R-r$

$$d= 20 cm-8 cm$$ 

$$d= 12 cm$$

We know that,  

Slant height of the frustum $𝑙 = \sqrt{ℎ² + 𝑑²}$

$\Rightarrow 𝑙 =\sqrt{ 16² + 12²}$

$\Rightarrow 𝑙 = \sqrt{256 + 144}$

$\Rightarrow 𝑙 = \sqrt{400}$

⇒ 𝑙 = 20 𝑐𝑚

Hence slant height of the cone is 20 𝑐𝑚.