A milk container of height 16 cm is made of metal sheet in the form of a frustum of a cone with radii of its lower and upper ends as 8 cm and 20 cm, respectively. Find the cost of milk at the rate of ` 22 per L which the container can hold.

Clearly, Given container is in the form of frustum of a cone.

As we know

Volume of frustum of a cone

Where, h = height, r₁ and r₂ are radii of two ends (r₁ > r₂)

For given bucket,

Radius of lower end, r₂ = 8 cm

Radius of upper end, r₁ = 20 cm

Height of container, h = 16 cm

Using these values,

We have.

⇒Volume = 1/3 × 22/7 × 16 × (64 + 400 + 160)

⇒Volume = 10459.42 cm³

As 1000 cm³ = 1 L

10459.42 cm³ = 10.45942 L = 10.46 L [Appx]

Also,

Cost for 1 L milk = 22 Rs

Cost for 10.46 L milk = 22(10.46) = 230.12 Rs