Surface Areas and Volumes Class 9 Notes Maths - Chapter 13

Chapter: 13

What Are Surface Areas And Volumes ?

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.