NCERT Class 9 Solutions: Surface Areas and Volumes (Chapter 13) Exercise 13.7 – Part 3
Q6 The volume of a right circular cone is . If the diameter of the base is , find

Height of the cone

Slant height of the cone

Curved surface area of the cone
Solution:

Diameter of the base of the cone
Therefore radius ( )
Let the height of the cone be

Radius
Height
Let the slant height of the cone be , than







Given,

Radius

Slant height
Therefore curved surface area
Q7 A right triangle with sides , and is revolved about the side . Find the volume of the solid so obtained.
Solution:
Note than when right triangle is revolved we get a cone with the same radius as the base of the right triangle.
Height is .
In triangle

Base is

Height is .
Cone so obtained has radius r = 5 cm and height 12 cm. Its volume,


