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Sphere:
A sphere is a three-dimensional figure obtained by the revolution of a semicircle about its diameter as an axis.
![shutterstock_1712835637 (1).jpg](https://resources.cdn.yaclass.in/78268b11-e721-4e40-b081-cd99c6a27f35/shutterstock17128356371w300jpg.jpg)
Volume of a sphere:
Let \(r\) be the radius of a sphere.
Volume of a sphere \(=\) cu. units
![shutterstock_1885382680 (1).jpg](https://resources.cdn.yaclass.in/6232293d-393e-4f17-b62f-d8b9cc75b4dd/shutterstock18853826801w300jpg.jpg)
Demonstration of the volume of a sphere using right circular cones:
Let us take a sphere and two right circular cones of the same base radius and height.
![sp_cone (1).png](https://resources.cdn.yaclass.in/f18a3b2a-c8c2-41a6-abdd-cbf9e7e56555/spcone1w500.png)
Radius of a sphere \(=\) \(r\) units
Radius of two cones \(=\) \(r\) units
Height of a sphere \(=\) Diameter \(=\) \(2r\)
Height of each cone \(=\) Height of a sphere \(=\) \(2r\)
Volume of a sphere \(=\) Volume of \(2\) cones
\(=\)
\(=\) [Since \(h = 2r\)]
\(=\)
Volume of a sphere \(=\) cu. units
Volume of a hollow sphere / spherical shell (volume of the material used):
![hol_sp (1).png](https://resources.cdn.yaclass.in/041c9c35-4c0b-4c70-8ef8-cc6a35f6ca11/holsp1w400.png)
Let \(r\) be the inner radius and \(R\) be the outer radius of the hollow sphere.
Volume of a hollow sphere \(=\) Volume enclosed between the outer and inner spheres
\(=\) \(-\)
\(=\)
Volume of a hollow sphere \(=\) cu. units
Important!
The value of \(\pi\) should be taken as unless its value is shared in the problem.