# NCERT Class 9 Solutions: Surface Areas and Volumes (Chapter 13) Exercise 13.2 – Part 2

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)

• 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 height

• Painting rate

Curved surface

Total cost of painting

• (Painting rate )

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

1. Its inner curved surface area,

2. The cost of plastering this curved surface at the rate of

Solution:

Circular well radius The well depth Plastering rate

1. Curved surface

2. 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: