1. "A hollow cylindrical iron pipe is 6 meters long. The internal and external diameters of the pipe are 3.5 cm and 4.2 cm respectively. Calculate the amount of iron used in the pipe. If the weight of iron is 5 kg per cubic decimeter, calculate the weight of the pipe."

2. "A hollow cylindrical iron pipe is open at both ends. The external diameter of its mouth is 30 cm, the internal diameter is 26 cm, and the length of the pipe is 14.7 metres. If tar is applied to its entire surface at the rate of ₹2.25 per square decimetre, calculate and write the total cost."

3. In front of Anowar's house, there is a solid iron pillar with a cylindrical lower part and a conical upper part. The diameter of the base is 20 cm, the height of the cylindrical part is 2.8 meters, and the height of the conical part is 42 cm. If the weight of 1 cubic centimeter of iron is 7.5 grams, then calculate and write the total weight of the iron pillar.

4. A hollow cylindrical iron pipe open at both ends has an inner radius and outer radius of 4 cm and 5 cm respectively. If the total surface area of the pipe is 1188 square centimeters, what is the length of the pipe?

5. A wooden box with a 5 cm thick lid is made from wooden planks. Its weight is 115.5 kg, and when filled with rice, it weighs 880.5 kg. The internal length and breadth of the box are 12 decimeters and 8.5 decimeters respectively, and the weight of rice per cubic decimeter is 1.5 kg. **(1) Calculate and write the internal height of the box.** **(2) At a rate of ₹1.50 per square decimeter, calculate the total cost to paint the outer surface of the box (excluding the base).**

6. A hollow vertical cylindrical iron pipe has an outer radius of 5 cm and an inner radius of 4 cm. If the total surface area of the pipe is 1188 square cm, calculate the length of the pipe.

7. The outer radius and inner radius of a hollow sphere made of iron are 21 cm and 7 cm respectively. If the weight of iron is 30 grams per cubic centimeter, what is the weight of the sphere?

(a) 2112.12 kg (b) 2212.21 kg (c) 1121.12 kg (d) 1122.21 kg

8. To make a hollow cylindrical pipe of uniform thickness, a solid iron sphere of radius 6 cm is melted. The pipe has a length of 18 cm and an outer radius of 10 cm. Find the thickness of the pipe.

9. A hollow cylindrical iron pipe, open at both ends, has a height of 2.8 meters. The inner circumference of the pipe is 4.6 decimeters, and it is made of 84.48 cubic decimeters of iron. Find the outer circumference of the pipe.

10. "A hollow cylindrical iron pipe is open at both ends. Its height is 2.8 metres, the internal diameter is 4.6 decimetres, and it is made of 84.48 cubic decimetres of iron. Calculate and write the external diameter of the pipe."

11. The difference between the outer and inner curved surface areas of a hollow cylindrical pipe is 44 square centimeters, and the length of the pipe is 14 cm. The volume of the material of the pipe is 99 cubic centimeters. Find the outer and inner radii of the pipe.

12. A vertical hollow cylindrical pipe made of iron has both ends open. Its height is 35 cm, the outer radius is 12 cm, and the inner radius is 10 cm. What is the volume of iron in the pipe in cubic centimeters?

13. A hollow vertical cylindrical iron pipe has an outer radius of 5 cm and an inner radius of 4 cm. If the total surface area of the pipe is 1188 square cm, what is the length of the pipe?

14. The internal length, breadth, and height of a tea box are 7.5 decimeters, 6 decimeters, and 5.4 decimeters respectively. The weight of the tea-filled box is 52 kg 350 g. If the weight of the empty box is 3.75 kg, calculate and write the weight of tea per cubic decimeter.