The document discusses calculating the perimeter of different shapes. It explains that the perimeter is the distance around the edges of a shape. To find the perimeter of a rectangle, you need to know the length and width, and then add them together. It provides examples of calculating perimeters of rectangles and squares by adding up the side lengths. The key steps to find perimeter are to identify the measurements of the sides and then add them together.

1. PERIMETER

2. PERIMETER
The perimeter of a shape is the
distance all the way around its
edges.

3. PERIMETER
The measurements needed to
calculate a perimeter depend
on the shape and there are
many different shapes.

4. PERIMETER
In order to find the perimeter of a
rectangle you must first find the
length and the width.
?
?

5. PERIMETER
Length is usually the longest side of
a rectangle

6. PERIMETER
Width is usually the shortest side of
a rectangle

7. PERIMETER
Lets look at a few and see if it’s the
width or the length.
If its width put your finger on your
nose.
If its length put your hand on your
head.

8. PERIMETER

9. Example 1: the diagram
represents a pen for Jim’s pigs.
How much fencing does he need
to go around the plot?
4
m
4m
5m
5m

10. Here the length is 5m and the
width is 4m.
The perimeter of the plot is
5+4+5+4 =18.
So he needs 18m of fencing.
4
m
4m
5m
5m

11. Example 2: The diagram
represents a pond that needs a
low railing round the boundary.
Sally is working out the perimeter.
80cm
1.2m
Caution: all measurements used in
the calculation must be the same
units.

12. So we know that 100cm = 1m
There are 2 zeros so we move
the decimal point 2 places to the
left.
80cm becomes 0.8m
80cm
1.2m
Caution: all measurements used in
the calculation must be the same
0.8m

13.  Now that our numbers all have the same
units we can add.
1.2m
0.8m
1.2 + 0.8 +1.2 + 0.8 = 4.0
So the perimeter is 4m. Don’t forget
to label your answers!

14. RECTANGLES AND SQUARES
 In a rectangle the opposite sides are equal,
so to work out the perimeter of a rectangle
you just need to know the length and width.
15cm
6cm
What is the length and what is the width?

15. PERIMETER
 There are three different methods to finding
the perimeter.
 Method 1: add all the numbers together.
15cm
6cm 6cm
15cm
15 + 6 + 15 + 6 = 42cm

16. PERIMETER
 Method 2: Because opposite sides are equal
you can also work out the perimeter in this
way: double the length, double the width,
then add the results together.
15cm
6cm 6cm
15cm
(15 X 2) + 6 X 2) = 30 + 12 = 42cm

17. PERIMETER
 Method 3: The last method just adds the
length and width then doubles it.
15cm
6cm 6cm
15cm
15 + 6 = 21 21 X 2 = 42cm

18. PERIMETER
 The method you choose is up to you- each
one will give the same answer.
 Lets see what you have learned. Find the
answer to each question.
 Once you have found the answer put you
hands on you head like this so I know your
finished.

19. PERIMETER
18m
6m
6 + 6 + 18 + 18 = 48 m

20. PERIMETER
8cm 8cm
10cm
8 + 8 + 10 = 26cm

21. PERIMETER
 A square
10m
10 X 4 = 40 m

22. PERIMETER
 Homework page 59