Question

A drinking glass is in the shape of frustum of a cone of height 21 cm with 6 cm and 4 cm as the diameters of its two circular ends. Find the capacity of the glass.

Answer 1

Let R and r be the radii of the top and base, respectively, of the drinking glass and let its height be h.

Then, `R =>  6/2 "cm" = 3  "cm", "r" => 4/2 "cm" = 2 "cm", h=21 "cm" `

Capacity of the glass = Capacity of the frustum of the cone

`=(pi"h")/3["R"^2+"r"^2+"Rr"]`

`=22/7xx1/3xx21xx[(3)^2+(2)^2+(3xx2)]"cm"^3`

= (22 × 19) cm³

= 418 cm³