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 < 21 per litre. [Use  =

7

22

]

Answer 1

Given.....Height of frustum of a cone = h = 24 cm
Radius of lower end = r = 8 cm
Radius of upper end = R = 20 cm
Volum of frustum of cone V = (πh) / 3 x (R + Rr + r )
V = (π24) / 3 x (20 + 20x8 + 8 )
V = 176 / 7 x 624
V = 176 x 89.142 cm
V = 15688.992 cm
V = 15688.99 cm / 1000
V = 15.6889 litre
Cost of milk per litre fill the container = 21 Rs
∴ Total cost of milk fill the container = 15.6889x21 = 329.4Rs ≃ 330 Rs.(approx.)

This is My solution...I think it's correct!...Hope it helps!
Thank You!