Chapter Notes: Mensuration

# Mensuration Class 6 Notes Maths Chapter 9

## What is Mensuration?

Mensuration is a branch of mathematics that is a topic in Geometry. It is a study of various geometrical shapes, their length, breadth, volume, and area for 2D as well as 3D shapes.

Some important terminologies included in this topic are covered below.

## Perimeter

Perimeter is the distance covered along the boundary forming a closed figure when we go around the figure once. The concept of the perimeter is widely used in real life. For Example:

1. For fencing land.
2. For building a compound wall around a house.

### Closed figure

• A figure with no open ends is a closed figure.
• Regular closed figures: A closed figure with all sides and angles equal.
• The perimeter of a regular closed figure is equal to the sum of its sides.

### Perimeter of a Rectangle:

= 2 (l + b)

Example 1:  A rectangle has a length of 5 units and a breadth of 3 units.
Solution:

= 2(5 + 3)
= 2(8)

= 16 units

Example 2: A rectangular garden has a length of 15 meters and a breadth of 7 meters. Find the perimeter of the garden.

The perimeter of a rectangle is given by the formula P = 2(l + b), where l is the length and b is the breadth.
l = 15 meters
b = 7 meters
So, the perimeter is P = 2(15 + 7)
= 2(22)

= 44 meters

Question for Chapter Notes: Mensuration
Try yourself:A rectangle has a length of 6 units and a breadth of 4 units. Find the perimeter.

### Perimeter of a Square:

= s + s + s + s

= 4 x S

Example 1: A square has a side length of 4 units.

Perimeter = 4 * side
length = 4 * 4

= 16 units

Example 2: A square photo frame has a side length of 8 centimeters. Find the perimeter of the photo frame.

The perimeter of a square is given by the formula P = 4s, where s is the side length.
s = 8 centimeters
So, the perimeter is P = 4(8)
= 32 centimeters

### Perimeter of an Equilateral triangle:

A triangle with all its sides and angles equal is called an equilateral triangle.

The perimeter of an equilateral triangle with the side 'a'=a+a+a =3 x a

Example 1: An equilateral triangle has a side length of 6 units.

Perimeter = 3 * side length
= 3 * 6
= 18 units

Example 2: An equilateral triangle has a side length of 10 inches. Find the perimeter of the triangle.

The perimeter of an equilateral triangle is given by the formula P = 3s, where s is the side length.
s = 10 inches
So, the perimeter is P = 3(10)

= 30 inches

## Area

The amount of surface enclosed by a closed figure is called its area. The following conventions are to be adopted while calculating the area of a closed figure using a squared or graph paper.

• Count the fully-filled squares covered by the closed figure as one square unit or unit square each.
• Count the half-filled squares as half a square unit.
• Count the squares that are more than half-filled as one square unit.
• Ignore the squares filled less than half.

For example, the area of this shape can be calculated as shown:

• Area covered by full squares = 6 x 1 = 6 sq. units Area covered by half squares = 7 x ½ = 7/2= 3 ½ sq. units.
• Total area of the given shape = 6 + 3 ½ sq. units Thus, the total area of the given shape = 9 ½ sq. Units.

### Area of a Rectangle

The area of the rectangle can be obtained by multiplying the length by the breadth.

Area = length ( l ) × breadth ( b)

Example: Find the area of a rectangle with a length 8 units and breadth 5 units.

The formula for the area of a rectangle is
A = 8 × 5
A = 40 square units

### Area of a Square

The area of the square can be obtained by multiplying side by side.

Area of a square = Side × Side =Side2=a2, where a is the length of each side.

Example: Find the area of a square with a side length of 6 units.

The formula for the area of a square is
A = side × side
A = 6 × 6
A = 36 square units

Question for Chapter Notes: Mensuration
Try yourself:Find the area of a square with a side length of 5 units.

### Area of a Triangle

Area of triangle = (1/2) × base × height = (1/2) × b × h

Example: Find the area of a triangle with a base of 10 units and height of 4 units.

The formula for the area of a triangle is
A = (1/2) × base × height.
A = (1/2) × 10 × 4
A = 20 square units

## Summary

The document Mensuration Class 6 Notes Maths Chapter 9 is a part of the Class 6 Course Mathematics (Maths) Class 6.
All you need of Class 6 at this link: Class 6

## Mathematics (Maths) Class 6

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## FAQs on Mensuration Class 6 Notes Maths Chapter 9

 1. What is the formula for finding the perimeter of a rectangle?
Ans. The formula for finding the perimeter of a rectangle is 2 x (length + width).
 2. How can the area of a triangle be calculated?
Ans. The area of a triangle can be calculated using the formula 1/2 x base x height.
 3. What is the difference between perimeter and area?
Ans. Perimeter is the total distance around the outside of a shape, while area is the amount of space inside the shape.
 4. How can the area of a circle be calculated?
Ans. The area of a circle can be calculated using the formula π x radius^2.
 5. What is the formula for finding the perimeter of a circle?
Ans. The formula for finding the perimeter of a circle is 2 x π x radius.

## Mathematics (Maths) Class 6

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