Question

A container, open at the top, is in the form of a frustum of a cone of height 24 cm with radii of its lower and upper circular ends as 8 cm and 20 cm respectively. Find the cost of milk which can completely fill the container at the rate of Rs 21 per litre.

Answer 1

Sol :
h = 24 cm
lower end = r = 8 cm
upper end = R = 20 cm
V =$\frac{\pi \times h}{3}\times (R^2+R\times r+r^2)$
V = $\pi \times \frac{24}{3}\times ({20}^2+20\times 8+8^2)$
V = 176 / 7 x 624
V = 176 x 89.142 $c{m}^3$
V = 15688.992 $c{m}^3$
V = $\frac{15688.992c{m}^3}{1000}$
V = 15.688992 litre
Cost of milk per litre fill the container = 21 Rs
∴ Total cost of milk fill the container = 15.688992 x21 = 329.4688rs