Page 234 - ICSE Math 6

THINK SMART

1. Draw three rectangles with the same perimeter. Calculate and compare their areas.

2. Two opposite sides of a square are increased by 2 cm each and the other opposite sides are
decreased by 2 cm each. Give reasons why or why not the statements below are true.
(a) The perimeter of new figure is the same as that of the square.
(b) The area of new figure is the same as that of the square.

Individual Activity
Objective: To find area of a polygon using a dot paper or geoboard

Material required: Geoboard or a dot paper
Demonstration: The area of the given polygon can be
found by dividing it into smaller parts.

We know, area of a square of side 1 unit is 1 sq. unit and area of a triangle formed by dividing
1
this square into two equal halves is sq. unit each.
2

A
B
C Area of square
D = 1 unit
E
H
F G Area of triangle
1
= unit
2
Since, region A consists of 6 unit squares, its area is 6 square units. Find the area of other regions
and complete the following table.
Region A B C D E F G H Polygon

Area 6 1
2
(cm ) 2
Thus, area of the polygon is _________ square units.

Can you find the perimeter of the above polygon?
One method is by putting a thread along all the sides of a polygon on a geoboard, straightening
the thread and measuring it with a ruler. The perimeter of the given polygon is greater than 20
units. Why?

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