Mensuration Class 8 Notes Maths Chapter 11

Students can go through AP 8th Class Maths Notes Chapter 11 Mensuration to understand and remember the concepts easily.

Class 8 Maths Chapter 11 Notes Mensuration

→ Area of

1. a trapezium = half of the sum of the lengths of parallel sides × perpendicular distance between them.
2. a rhombus = half the product of its diagonals.

→ 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(r + h)

→ Amount of region occupied by a solid is called its volume.

→ Volume of
a cuboid = l × b × h
a cube = l³
a cylinder = πr²h

→ i) 1 cm³ = 1 mL
ii) 1L = 1000 cm³
iii) 1 m³ = 1000000 cm³
= 1000L

→ Perimeter, and area can be calculated for closed figures only.

→ Perimeter is the distance around the boundary of given closed figure.

→ Area is the region covered by the boundary of given closed figure and is expressed in square units.

→ Volume can be calculated for 3d figures like cube, cuboid, cone, etc….

→ Area of some known figures.
a) Triangle = \(\frac{1}{2}\)bh
b) Square = side × side
c) Rectangle = length × breadth
d) Equilateral triangle = \(\frac{\sqrt{3}}{4}\)a²
e) Trapezium = \(\frac{\mathrm{h}}{2}\) (a + b)
where a, b are lengths of parallel sides
f) Circle = πr²
g) Parallelogram = bh

→ Perimeter of
a) Triangle = sum of all sides
b) Square = 4 × side = 4s or 4a
c) Rectangle = 2(l + b)
d) Equilateral triangle = 3s
e) Circle = 2πr²
f) Parallelogram = sum of lengths of all four sides.