Mensuration Class 8 Notes- Chapter 11

What is Mensuration?

Mensuration is a branch of mathematics which mainly deals with the study of different kinds of Geometrical shapes along with its area, length, volume and perimeters. It is completely based on the application of both algebraic equations and geometric calculations. The results obtained by the Mensuration are considered very accurate. There are two types of geometric shapes:

  • 2D shapes: The solid figures or geometrical shapes having only its length and width are called as the 2D or two-dimensional shapes. It is a flat surface which has no thickness and height. Circle, Parallelogram, Rectangle, Rhombus, Square, Trapezoid and Triangle are examples of 2D shapes.
  • 3D shapes:The solid figures or geometrical shapes having length, breadth, height width, surface area and volume are called as the 3D or three-dimensional shapes. Cube, Cuboid, Cylinder, Cone, Hemisphere, Prism, Pyramid and Sphere Triangle are examples of 3D shapes.

Application of Mensuration

Mensuration is mainly used for calculating or finding the area, perimeter, volume and total surface area of geometrical shapes. Listed below are some important mensuration formulas:

    • To find an area of a rectangle

Area (A) = length (l) × breath (b) ⇔ A = l * b

    • To find the Perimeter of a rectangle

Perimeter (P) = 2 × Length (l) + Breath (b) ⇔ P = 2 × l + b

    • To find an area of a square

Area (A) = Length (l) × Length (l) ⇔ A = l * l

    • To find the Perimeter of a square

Perimeter (P) = 4 × Length (l) ⇔ P = 4 × l

    • To find an area of a triangle

Area of a triangle (A) = (Base(b) × Height(h)) / 2 ⇔ A = (b * h) / 2

 

Important Questions

  1. Find the side of a cube whose surface area is given as 900 cm².
  2. Calculate, how many sheets of metal is required to construct a closed cylindrical tank of height 4m and radius 9m.
  3. Find the height of a cuboid for a given volume – 325 cm³ and its base area is 35 cm².
  4. Find the height of the cylinder whose volume is 1.32 m³ and diameter of the base is 150 cm?
  5. Explain, what happens if each edge of a cube is doubled.

Learn more about the mensuration, 2d and 3d shapes, and mensuration formulas from the topics given below:

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