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E:\Working\Focus_Learning\Math_Genius_5_(05-10-2023)\Open_Files\CHAP_11
\\November 22, 2023 5:10 PM Surender Prajapati Proof 5 Reader _________________________ Date: ___________________74

1. Find the perimeter of the following figures.
(a) (b) 3.6 cm (c)
20 cm
5 cm 1.7 cm

23 cm 3.6 cm 3.6 cm 4.5 cm

3.6 cm
2. Find the area of the following.

(a) (b) (c)

perimeter

The distance around the edges of a closed figure is called perimeter. We know that a plane
figure bounded by only line segments is called a rectilinear figure. A triangle, rectangle and
square are rectilinear figures. The sum of the lengths of all sides of a rectilinear figure is
called its perimeter.

Look at some rectilinear figures and their perimeters. Let us know how we can find
perimeter of these figures.

perimeter of a rectangle
A D
In the given figure, ABCD is a rectangle in which AB, BC, CD and DA
are its sides. We know that the opposite sides of a rectangle are equal.
Perimeter of rectangle ABCD = AB + BC + CD + DA

= AB + BC + AB + BC B C
(Since AB = CD and AD = BC) = 2(AB + BC)

= 2 (Length + Breadth)

Perimeter of a rectangle = 2 (Length + Breadth)

example 1: Find the perimeter of a rectangle whose length is 12 cm and breadth is 7 cm.
Solution: Length of rectangle = 12 cm and breadth of rectangle = 7 cm

Perimeter of the rectangle = 2 (Length + Breadth) 12 cm
= 2(12 + 7) cm
= 2 × 19 cm = 38 cm 7 cm

Hence, the perimeter of the rectangle is 38 cm.
teacher’s Explain to students that they can also use the short form for any formula. Like perimeter of rectangle can also
tip be written as P = 2(l + b), where P stands for perimeter, l for length and b for breadth.

212 Mathematics-5