CBSE Class 6 — Notes, Chapters & Practice Quizzes

Chapter 6: Perimeter and Area

Summary

This chapter studies perimeter and area of plane figures. The perimeter of any closed figure is the distance covered along its boundary in one round; for a polygon it is the sum of all side lengths. The perimeter of a rectangle is \(2 \times (\text{length} + \text{breadth})\), of a square is \(4 \times \text{side}\), and of a triangle is the sum of its three sides; a regular polygon\u2019s perimeter is the number of sides times the length of a side. Area is the amount of region enclosed by a closed figure, measured in square units. The area of a rectangle is length \(\times\) breadth and the area of a square is side \(\times\) side. The chapter shows how to estimate areas of irregular shapes using squared or graph paper, counting full squares and half squares. A key result is that the area of a triangle is half the area of the rectangle that contains it, so the area of a right triangle is half of base \(\times\) height. Through tangram puzzles, house plans and area mazes, students see that two figures can have the same area but different perimeters, or the same perimeter but different areas.

Key terms

Important questions

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Deep Dive:

Estimate and Verify

Akshi says that the perimeter of this triangle shape is 9 units. Toshi says it can’t be 9 units and the perimeter will be more than 9 units. What do you think?

Write the perimeters of the figures below in terms of straight and diagonal units.

Find various objects from your surroundings that have regular shapes and find their perimeters. Also, generalise your understanding for the perimeter of other regular polygons.

Find out the length of the boundary (i.e., the perimeter) of each of the other arrangements below.

Arrange the two pieces to form a figure with a perimeter of 22 cm.

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Find the area of the following figures.

Let’s Explore! Why is area generally measured using squares?

Let’s Explore! On a squared grid paper (1 square = 1 square unit), make as many rectangles as you can whose lengths and widths are a whole number of units such that the area of the rectangle is 24 square units. a. Which rectangle has the greatest perimeter? b. Which rectangle has the least perimeter?

Area of a Triangle

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Making it ‘More’ or ‘Less’

House plan of Charan

House plan of Sharan

Area Maze Puzzles

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