NCERT Class 9 Solutions: Surface Areas and Volumes (Chapter 13) Exercise 13.2 – Part 2
Q4 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)

Q5 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 )

Q6 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
Q7 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 =
Q8 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