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

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Different types of shapes also its volume and total surface area formulas

Different Types of Shapes

Different types of shapes also its volume and total surface area formulas

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 )

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:

Formulas for surface area and volume of a cylinder

Surface Area and Volume of a Cylinder

Formulas for surface area and volume of a cylinder

  • The pipe radius

  • The pipe length

Total radial surface or curved surface area of the pipe