# Surface Areas and Volumes Class 9 Notes Maths - Chapter 13

## Chapter: 13

## What Are Surface Areas And Volumes ?

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## Cone

Whose radius = r, height = h, Slant height = l

- Short lenght (l) = √(r
^{2}+ h^{2})

- Curved surface area = πrl
- Volume = (1/3)πr
^{2}h - Total surface area = πr(l + r)

## Sphere

Whose radius = r

- Surface Area = 4πr
^{2} - Volume =(4/3)πr
^{3}

## Hemisphere

Whose radius = r

- Curved surface area = 2πr
^{2} - Total surface area = 3πr
^{2} - Volume =(2/3)πr
^{3}

## Points To Remember

- Cube has all the edges of same length.
- Volume =(2/3)πr
^{3} - In cuboid one of the dimension (length, bredth or height) is different.
- In cube & cuboid, area of four faces (except top & bottom) is taken as lateral surface area.
- In cube & cuboid, area of all four faces, top & bottom is taken as total surface area.
- Area of the rectangle sheet is taken as the lateral surface of the cylinder.

- A solid generated by the revolution of right triangular surface about any one leg is called right circular cone.
- The height of the hemisphere is same as the radius of the hemisphere.