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

Surface Area And Volume Class 9 Notes Chapter 13

1. Cuboid: A figure which is surrounded by six rectangular surfaces is called cuboid.
The opposite surface of a cuboid is equal and parallel.

A cuboid has 12 edges and 8 corners. Each corner of a cuboid is called the vertex of a cuboid. The line segment joining the opposite vertices is called the diagonal of a cuboid. There are four diagonals in a cuboid.

Volume of cuboid = Length Ã— Breadth Ã— Height = l Ã— b Ã— h
Lateral surface area = 2 (Length + Breadth) Ã— Height = 2 (l + b) Ã— h
Total surface area = 2 (Length Ã— Breadth + Breadth Ã— Height + Height Ã— Length) = 2 (lb + bh + hl)
Total length of cuboid = 4 (l + b + h)

Surface Area And Volume Class 9 Notes Pdf Chapter 13

2. Cube: A cuboid, whose length, breadth and height are same is called a cube.
A cube has six surfaces, twelve edges, eight corners and four diagonals.
Volume of cube= (Side)3 = l3
Lateral surface area = 4 Ã— (Side)2 = 4l2
Total surface area = 6 Ã— (Side)2 = 6l2
Total length of cube = 12l
Diagonal of cube = âˆš3 l

3. Right Circular Cylinder: A right circular cylinder is considered as a solid generated by the revolution of a rectangle about one of its sides.

The volume of a cylinder = Ï€r2h
Curved surface area or lateral surface area = 2Ï€rh
Total surface area = Curved surface + 2 Ã— Base area = 2Ï€rh + 2Ï€r2 = 2Ï€r(h + r)

Class 9 Maths Chapter 13 Notes

4. Cone: A right circular cone is a solid generated by revolving of a triangle about one of its sides (other than hypotenuse).

Volume of cone = $$\frac { 1 }{ 3 }$$ Ï€r2h
Curved surface area or lateral surface area = Ï€rl
Total surface area = Curved surface area + Base area

Class 9 Surface Area And Volume Notes Chapter 13

5. Sphere: A solid which is surrounded by a curved surface and each point of the surface is the same distance from a fixed point. The fixed point is called the centre of the sphere. The line segment joining from the centre of the sphere to any point of the surface is called the radius of the sphere.

Surface Areas And Volumes Class 9 Notes Chapter 13

6. Hemisphere: A plane passing through the centre of a sphere divides the sphere into two equal parts. Each part is called a hemisphere.

Volume of hemisphere = $$\frac { 2 }{ 3 }$$ Ï€r3
The curved surface area of hemisphere = 2Ï€r2
Total surface area of hemisphere = 2Ï€r2 + Ï€r2 = 3Ï€r2

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