Mensuration - Revision Notes

CBSE Class 8 Mathematics
Revision Notes
Chapter – 11
Mensuration

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• Perimeter: Length of boundary of a simple closed figure.
  Perimeter of:
  Rectangle = 2(l + b)
  Square = 4a
  Parallelogram = 2(sum of two adjacent sides)
• Area: The measure of region enclosed in a simple closed figure.
• Area of a trapezium = half of the sum of the lengths of parallel sides × perpendicular distance between them.
• Area of a rhombus = half the product of its diagonals.
• Triangle = 12$\frac{1}{2}$ x base x height
• Diagonal of:
  Rectangle = l2+b2−−−−−√$\sqrt{l^2+b^2}$
  Square = 2a−−√$\sqrt{2a}$
• Surface area of a solid is the sum of the areas of its faces.
• Surface area of:
  
  a cuboid = 2(lb + bh + hl)
  
  
  a cube = 6l2
  
  
  a cylinder = 2πr$2\pi r$(r + h)
• Amount of region occupied by a solid is called its volume.
•  Volume of
  a cuboid = l x b x h
  a cube = l3
  a cylinder = π$\pi$r2h
• (i) 1 cm3 = 1 ml   
• (ii) 1L = 1000 cm3
• (iii) 1 m3 = 1000000 cm3 = 1000L