NCERT Class 9 Solutions: Surface Areas and Volumes (Chapter 13) Exercise 13.7 – Part 2

Formulas of cones: The base area of circle is=πr^2,and the volume is=1/3π r^2h

Understanding Cones and Slant Height

Formulas of cones: The base area of circle is=πr^2,and the volume is=1/3π r^2h

Q-3 The height of a cone is Equation . If its volume is Equation , find the radius of the base. (Use Equation )

Solution:

We are given,

  • Height (h) Equation

  • Volume = Equation

Consider, the radius of the base of cone to be Equation

Then, volume Equation

  • Equation

  • Equation

  • Equation

  • Equation

  • Equation

  • Equation

Q-4 If the volume of a right circular cone of height Equation is Equation , find the diameter of its base.

Solution:

Given,

  • Height Equation

  • Volume Equation

Consider, the radius of the base of the cone be Equation

Now, volume Equation

  • Equation

  • Equation

  • Equation

  • Equation

  • Equation

  • Equation

Q-5 A conical pit of top diameter Equation is Equation deep. What is its capacity in kiloliters?

Solution:

Given,

  • Diameter of the top of the conical pit Equation therefore, radius Equation

  • Depth of the pit Equation

Therefore, volume Equation

  • Equation

  • Equation

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