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) = √(r2 + h2)
- Curved surface area = πrl
- Volume = (1/3)πr2h
- Total surface area = πr(l + r)
Sphere
Whose radius = r
- Surface Area = 4πr2
- Volume =(4/3)πr3
Hemisphere
Whose radius = r
- 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.
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