Cl-5 (Math) | Ch-22 | Area

Table of Contents

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Pre-Requisites

Basic knowledge on triangle , square, circle , rectangle and bounded figures.

Learning Objective

On successful completion of this lesson, students will be able to:

demonstrate basic knowledge on area of bounded figures.
analyze the bounded figures and their area.
develop problem-solving skills.
apply in real life.

Dictionary

Area: Bounded Surface
Picture: Figure
Graph: Grapgh or Sketch
Percentage: %age
Average: Mean
Numeral: Number
>: Greater than
<: Lesser than
=: Equal to
Ascending: Increasing
Descending: Decreasing
Order: Sequence

22.1 Introduction

22.1.1 Figure

=> Figure: Picture that we draw on a piece of paper is called a figure.

e.g:

=> Bounded figure: Closed figure is called a bounded figure.

e.g:

22.1.2 Area

=> Area: The measure of the amount of surface enclosed by a closed figure is called its area.

e.g1: Rectangle , Square , Triangle , Polygon, Circle etc.

22.1.3 Comparison of areas

=> Similar figures: Area ∝ Size

=> Different figures: Find areas of the both figures and compare by their values of the areas i.e Area ∝ Value

22.1.4 Unit of Area

1.Square metre: Let’s a square having 1 metre of each side.

=> Area = 1 square metre or 1 sq.m or 1 m².

2. Square centimetre: Let’s a square having 1 centimetre of each side.

=> Area = 1 square centimetre or 1 sq.cm or 1 cm².

22.2 Area of a Rectangle

=> Let’s a Rectangle whose length is l amd breadth is b.

Then,

Formula

Area of a Rectangle

A = (l x b) sq. unit

l = A/b unit

b= A/l unit

22.3 Area of a Square

=> Let’s a Square whose side is s.

Then,

Formula

Area of a square

A = (s x s) sq. unit

Solved Examples

Ex1. Find area of a Rectangle whose length is 10 m and breadth is 5 m.

Sol. Given that:

l = 10 m

b = 5 m

A = (l x b) sq. unit = (10 x 5) sq.m = 50 sq.m ans.

Ex2. Find area of a square whose side is 5 m.

Sol. Given that:

s = 5 m

A = (s x s) sq. unit = (5 x 5 ) sq.m = 25 sq.m ans.