The quantity of iron sheet to make a boya of right circular conical shape is 75 3/7 m sq. If the slant height of it is 5cm, then let us write, by calculating, the volume of air in the boya and its height. Let us determine the expenditure to color the whole surface of the boy a at the rate of ₹ 2.80 per m. the width of the iron-sheet not to be considered while calculating.