The cost of papering the four walls of a room at 75 paise per square metre is ₹ 240. The height of the room is 5 metres. Find the length and the breadth of the room, if they are in the ratio 5 : 3.

The area of a playground is 3650 m². Find the cost of covering it with gravel 1.2 cm deep, if the gravel costs ₹ 6.40 per cubic metre.

The external dimensions of a closed wooden box are 27 cm, 19 cm and 11 cm. If the thickness of the wood in the box is 1.5 cm; find :

(i) volume of the wood in the box;

(ii) the cost of the box, if wood costs ₹ 1.20 per cm³;

(iii) number of 4 cm cubes that could be placed into the box.

A tank 20 m long, 12 m wide and 8 m deep is to be made of iron sheet. It is open at the top. Determine the cost of iron-sheet, at the rate of ₹ 12.50 per metre, if the sheet is 2.5 m wide.