an open metal bucket is in the shape of a frustum of a cone of height 21cm with radii of its lower and upper ends as 10cm and 20cm respectively.find the cost of milk which can completely fill the bucket at Rs.30 per litre.[use pie=22/7]

Height of frustum, h = 21 cm

Radius of lower end, r = 10 cm

Radius of upper end, R = 20 cm

Volume of frustum = 1/3 * pi * h * (R² + r² + Rr)

Put in the values to get the volume as 15.4 litre.

Thus, the cost of milk that can completely fill the bucket is Rs (30 x 15.4) = Rs 462