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)
    CONE
    • Curved surface area = πrl
    • Volume = (1/3)πr2h
    • Total surface area = πr(l + r)

    Sphere

    SPHERE

    Whose radius = r

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

    Hemisphere

    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. 
    POINTS TO REMEMBER
    • 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.