Mensuration | Mental Mathematics for Class 8 PDF Download

Introduction

Perimeter: A simple closed figure's perimeter is the length of its boundary.
Rectangle = 2(l+b)
Square = 4a
Parallelogram = 2 (sum of adjacent sides)

• Area: The size of a territory encompassed in a simple closed figure is referred to as its area.
• The area of a trapezium is equal to half of the sum of the parallel sides' lengths divided by the perpendicular distance between them.

Area of a rhombus = half the product of its diagonals.

Diagonal of:
Square = √2a

• A solid's surface area is equal to the sum of its face areas.

Surface area of cuboid = 2(lb+bh+lh)
Surface area of cube = 6l²
Surface area of a cylinder = 2πr(r+h)
The volume of a solid is the amount of space it takes up.
Volume of
a cuboid = l×b×h
a cube = l³
a cylinder = πr²h
Few basic measurements value are as follows:
(i)1cm³ = 1mL
(ii)1L = 1000cm³
(iii)1m³ = 1000000cm³
=1000L

Mensuration Important Formulas

Some important Mensuration formulas are discussed below:

• Area of Trapezium

½ of the sum of the length of parallel sides * Perpendicular distance between them.

• Surface Area of Cuboid  - 2 (LB + BH + HL)  or  2 (Length * Breadth + Breadth * Height + Length * Height )
• Surface Area of Cube - 6 * side²
• Surface Area of Cylinder - 2radius ( radius + height)
• Volume of Cuboid -  LBH or (Length  * Breadth * Height)
• Volume  of Cube - Side³
• Volume of Cylinder - πr²h
• In the above formula
• H - Height of cylinder