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

## What Are Surface Areas And Volumes ?

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## Cone

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

• Short lenght (l) = √(r2 + h2)
• Curved surface area = πrl
• Volume = (1/3)πr2h
• Total surface area = πr(l + r)

## Sphere

• Surface Area = 4πr2
• Volume =(4/3)πr3

## Hemisphere

• Curved surface area = 2πr2
• Total surface area = 3πr2
• Volume =(2/3)πr3

## Points To Remember

• Cube has all the edges of same length.
• Volume =(2/3)πr3
• 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.