A cuboid has total surface area of 50 m² and lateral surface area os 30 m². Find the area of its base.

Show that the product of the areas of the floor and two adjacent walls of a cuboid is the square of its volume.

The walls and ceiling of a room are to be plastered. The length, breadth nad height of the room are 4.5 m, 3 m and 350 cm, respectively. Find the cost of plastering at the rate of Rs. 8 per square metre.

A classroom is 7 m long, 6 m broad and 3.5 m high. Doors and windows occupy an area of 17 m². What is the cost of white washing the walls at the rate of Rs. 1.50 per m².

The central hall of a school is 80 m long and 8 m high. It has 10 doors each of size 3 m ×1.5 m and 10 windows each of size 1.5 m× 1 m. If the cost od white washing the walls of the hall at the rate of Rs. 1.20 per m² is Rs. 2385.60, find the breadth of the hall.