Page 133 - ICSE Math 4

Example 3: Find the area covered by the given fi gure PQRS.
P Q
Solu on: Number of squares covered by the fi gure PQRS = 25

Area of 1 square = 1 square unit
Area of 25 squares = 25 × 1 square unit
S R
= 25 square units
So, the area covered by the fi gure is 25 square units.

Area of Irregular Plane Figures

Irregular plane fi gures do not have a fi xed shape, thus, we can fi nd only the approximate
area of such fi gures.

To fi nd the area of irregular plane fi gures, we follow the given steps.
Trace the outline of the given irregular plane fi gure on squared sheet paper where each
square has an area of 1 square unit.

1 1
• If the shape covers a square, the area is taken as square unit.
2 2

1
• If the shape covers more than a square, the area is taken as 1 square unit.
2
1
• If the shape covers less than a square, then that square is le out.
2
• Find the total number of squares to obtain the approximate area of the given irregular
plane fi gure.

Let’s understand how to fi nd the area of irregular plane fi gures with the help of the
following example.

Example 4: Find the approximate area of the given fi gure. ab
Solu on: Number of whole squares = 1, 2, 3 and 4, i.e., 4
I 1 2 III
Number of half squares = a and b, i.e., 2 II 4 3 IV

Number of squares that are covered more than half A B

= A and B, i.e., 2
Number of squares that are covered less than half = I, II, III and IV,

i.e., 4 (Neglect these squares.)

 Approximate area of the given fi gure
1
= (4 × 1 square unit) + (2 × square unit) + (2 × 1 square unit)
2
= 4 square units + 1 square unit + 2 square units = 7 square units

So, the approximate area of the given fi gure is 7 square units.

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