# NCERT Class 9 Solutions: Surface Areas and Volumes (Chapter 13) Exercise 13.7 – Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q-6 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:

I. Diameter of the base of the cone

Therefore radius ()

Let the height of the cone be

- Now, volume of the cone =

II. Radius , Height , Let the slant height of the cone be , then

III. Given,

- Radius
- Slant height

Therefore, curved surface area

Q-7 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,