Page 154 - Math Skill - 4

152 Maths

2. Find the perimeter of the square whose side is:

(a) 17 cm (b) 21 cm (c) 19 m
3. The side of square lawn is 13 m. Find the length of fence around it.
4. The length and the breadth of a rectangular field are 83 m and 62 m respectively. If Ankit
walks around the field once, what distance is covered by him?

5. Vidushi draws a square of side 15 cm and a rectangle
of length 20 cm and breadth 15 cm. Which has a greater 80 m
perimeter and by how much? carrot

6. A farmer grows carrot and radish in his field as shown in 25 m 70 m
the figure. Find the perimeter of both the parts. Are they 10 m
equal?
radish 10 m 20 m
Area

It is defined as the total space occupied by a flat surface or shape of an object.
Now look at the figures given aside :
It is clear that Fig. 2 occupies more surface than Fig. 1.
Thus, we can say that Fig. 2 has more area.

Area is measured in square units of length.
(i) Area of smaller objects such as a book or a geometry
box is measured in square centimetres. Fig. 1 Fig. 2

(ii) Area of bigger surfaces such as playgrounds is measured in square metres.
The standard unit of measuring area is a square of unit size. 1 cm

A square centimetre (or sq cm) is the area of a square of side 1 cm. 1 cm 1 cm
It has an area of 1 sq cm. 1 cm
Now, look at the square.

The area of this square is 9 square centimetres because it has 9 squares of
area 1 sq cm each.

Area of a Rectangle

Look at the rectangle. What is the area of this rectangle?

Let us count the number of squares enclosed. There are 12 squares
enclosed.

Thus, area of the rectangle = 12 sq cm = 4 × 3 sq cm 3 squares
= length of the rectangle × breadth of the rectangle
4 squares
Thus, Area of a rectangle = length × breadth

Area of a Square

Look at the square which is divided into 9 smaller squares.