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Example 3: Find the area of a rectangle whose length and breadth are 18 cm and 11 cm respectively.

Solution: Length of the rectangle, l = 18 cm
Breadth of the rectangle, b = 11 cm
Area of the rectangle = length (l) × breadth (b) = 18 cm × 11 cm = 198 sq. cm
Example 4: Find the area of a square plot of side 14 m.
Solution: Side of the square, a = 14 m
2
We have, area of the square = (side) = (14 m) 2
= 14 m × 14 m = 196 sq. m

Example 5: If the length, width, and height of a room are 7 m, 8 m, and 6 m respectively.
Find the total area of four walls.
Solution: Length of the room, l = 7 m,
Width of the room, b = 8 m h

Height of the room, h = 6 m l b
Area of four walls of room can be calculated by using the formula:
Area of four walls of a room = 2 × (length + breadth) × height sq. units
Area of four walls of a room = 2 × (l + b) × h

= 2 × (7 + 8) m × 6 m Quick Check
= 2 × 15 × 6 sq. m = 180 sq. m Calculate the area of
Thus, the total area of the four walls is 180 sq. m 4-walls of your classroom.

Maths Talk
Rubeena is making a collage photo frame, and for completing it, she needs
a square of side 5 cm. She has a rectangular sheet of length 24 cm and 5 cm
breadth 17 cm. She cuts off a square of side 5 cm from the rectangular 17 cm
sheet as shown in figure. What do you say that the total length of side
increased after cutting off the square? 24 cm
Has the perimeter of the sheet increased or decreased now?
Rubeena needs one more square of the same size, so she cuts off from the
opposite side of the sheets as shown in the figure. 5 cm
Will the perimeter of the remaining sheet increase further? 5 cm
Will the area increase or decrease further?

Example 6: A door frame of dimensions 4 m × 3 m is fixed on the wall of dimension 12 m × 12 m.
2
Find the total labour charges for painting the wall if the labour charges for painting 1 m of the
wall is `12.50.
Solution: Painting of the wall has to be done excluding the area of the door.

2
Area of the door = l × b = 4 × 3 m = 12 m 2
2
Area of wall including door = side × side = 12 m × 12 m = 144 m
2
Area of wall excluding door = (144 − 12) m = 132 m 2
Since, the labour charges for painting 1 m of the wall is `12.50.
2
Therefore, the total labour charges for painting the wall = `(12.50 × 132) = `1650

283 Perimeter and Area