In this question, we have to find two things
(i) Cost of oil which can completely fill the container at the rate of rs. 50 per litre.
(ii) Cost of metal used, if it costs rs. 5 per 100 cm2.
And we are given an open container made up of a metal sheet which is in the form of a frustum of a cone whose height is 8 cm and radii of its lower and upper ends as 4 cm and 10 cm respectively.
This is very important questions for 10th boards exam. Here in mensuration chapter, we have to learn many formulas can someone give a trick or shortcut for these formulas.