This document provides a lesson on calculating the perimeters of polygons. It begins by defining a polygon and perimeter. Students are shown how to calculate the perimeter of a rectangle by adding the length and width measurements. The formula for a rectangle's perimeter, 2 x length + 2 x width, is introduced. Other shapes where not all side measurements are needed, like squares, are discussed. Finally, students are given a challenge to calculate the perimeter of a more complex shape and express it in words and letters.

1. CLASS-V
SUB-MATHS
LO: To measure and
calculate perimeters of
polygons
Some of the clip art used in this presentation is licensed from the Clip Art Gallery on DiscoverySchool.com

2. Talk Partners‟
• What are polygons?
• How many types can you list?

3. Look at this „L‟ shape:
• How would you
calculate the
distance around
this shape?
• What is the
correct
mathematical term
for this?

4. Perimeter
• When we measure the distance
around a shape, we call it the
perimeter.
• We measure the perimeter using the
length and breadth measurements

5. The perimeter is found by adding up all
the length and breadth measurements.
+ +
+ +
Length
Length
Breadth
Breadth

6. Can you find the perimeter for
this shape?
12 cm
12 cm
5cm 5cm

7. Answer
Add up all the length and breadth
measurements:
12cm + 12cm + 5cm + 5cm
= 34cm!

8. • We can write this in another way:
“Twice the length plus twice the
breadth”
• This is often written as:2 X l + 2 X b
• Can you tell me why?

9. When calculating the perimeter
of a rectangle do we need to
measure all the side?
Talk Partners’ about your ideas
and be ready to feedback to
class!

10. • Can you think of any other shapes
where you would not need to measure
every side in order to work out the
perimeter?
• Can you express the
perimeter of these shapes
in words and in letters?

11. CHALLENGE:
Can you find the perimeter for this shape?
7
c
m
7
c
m
5cm
5cm
3
c
m
3
c
m
3
c
m
3
c
m
3cm 3cm
3cm 3cm

12. How did you work
out the answer?
Can you express
this perimeter in
words and letters?

13. THANKS
PREPARED BY
PUNEET KUMAR
(KV 1 A. CANTT)