# NCERT Class 9 Solutions: Surface Areas and Volumes (Chapter 13) Exercise 13.2 – Part 2 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q-4 The diameter of a roller is and its length is . It takes complete revolutions to move once over to level a playground. Find the area of the playground in . Solution:

- The roller length is (h)
- The cylinder radius is
- Total no. of revolutions
- Distance covered by roller in one revolution

- Area of the playground
- ( complete revolutions to level a playground)

Q-5 A cylindrical pillar is in diameter and in height. Find the cost of painting the curved surface of the pillar at the rate of . Solution:

- The pillar radius
- The pillar height
- Painting rate
- Curved surface
- Total cost of painting
- (Painting rate )

- Curved surface

Q-6 Curved surface area of a right circular cylinder is . If the radius of the base of the cylinder is , find its height. Solution:

- The radius of the base r and the height of the cylinder h.
- Area of a right circular cylinder is

Curved surface area

Q-7 The inner diameter of a circular well is . It is deep. Find

- Its inner curved surface area,
- The cost of plastering this curved surface at the rate of

Solution:

Circular well radius The well depth Plastering rate

- Curved surface
- Cost of plastering =

Q-8 In a hot water heating system, there is a cylindrical pipe of length and diameter . Find the total radiating surface in the system. Solution:

- The pipe radius
- The pipe length

Total radial surface or curved surface area of the pipe