1. Perimeter Of Shapes.
8cm
2cm
5cm
3cm A1 A2
16m
12m
10m
12cm
7cm

2. What Is Perimeter ?
Perimeter is the distance around a shape. Think of a fence.
9cm
4cm
4cm
9cm
For example:
Perimeter = = 26 cm

3. Area Of Shapes.
8cm
2cm
5cm
3cm A1 A2
16m
12m
10m
12cm
7cm

4. What Is Area ? Area is the amount of space inside a shape: Area Area
1cm
Area is measured in square units.
1cm2
A square unit is a square measuring one unit in each direction. For example:
It is written as :

5. Estimating The Area. B A C D
Look at the four shapes below and use your judgement to order them from smallest to largest area: A B C D

6. B A C D To decide the order of areas consider the four shapes again:
To measure the area we must determine how many square centimetres are in each shape:
Each shape is covered by 36 squares measuring a centimetre by a centimetre .We can now see that all the areas are equal at 36cm2 each.

7. Area Of A Rectangle. C Length Width
The formula for the area of a rectangle is:
A = LW
for short.
Area = Length x Width or

8. We can now calculate the area of each rectangle very quickly:
(1)
(2)
A= L x W
A = 12 x 3 =36cm2
(3)
A= L x W
A = 6 x 6 =36cm2
A= L x W
A= L x W
(4)
A = 18 x 2 =36cm2
A = 9 x 4 =36cm2

9. Example 1
Calculate the area of the rectangle below:
(2) 3m 5m
7cm
4cm
(1)
Solution
This area is in square metres: 1m
A = LW
Solution
A = LW
L = 7
W = 4
L = 3
W = 5
A = 7 x 4
A = 3 x 5
A = 28cm2
A = 15m2

10. Example 3.
Solution.
8cm
2cm
5cm
3cm
Split the shape up into two rectangles: A1
Calculate the area of A1 and A2. A2 2 A1 A2 3 5 6
Calculate the area of the shape above:
Area = A1 + A2
Area = ( 2 x 5) + (6 x 3)
Area =
Area = 28cm2

11. What Goes In The Box ? Find the area of the shapes below : (1) 8cm 6cm
(2)
48cm2
(3)
17cm
8cm
12cm
5cm
11.34m2
141cm2

12. The Area Of A Triangle. Consider the right angled triangle below: 5cm
Base
Height
What shape is the triangle half of ?
The formula for the area of a triangle is:
Rectangle
Area = ½ x Base x Height
What is the area of the rectangle?
A = ½ BH
Area = BH

13. Does the formula apply to all triangles ?
Base (B)
Height (H)
Can we make this triangle into a rectangle ?
Yes
The triangle is half the area of this rectangle:
The areas marked A1 are equal. B H A1 A2
The areas marked A2 are equal.
For all triangles:
Area = ½ BH

14. Calculate the areas of the triangles below:
Example 1
Example 2
10cm
6cm
6.4m
3.2m
Solution.
Solution.
Area = ½ x base x height
Area = ½ x base x height
height = 6cm
base = 10 cm
height = 3.2m
base = 6.4m
Area = ½ x 10 x 6
Area = ½ x 6.4 x 3.2
Area = ½ x 60 = 30cm2
Area = ½ x = 10.24m2

15. Example 3.
Calculate the area of the shape below:
Solution.
16m
12m
10m
Divide the shape into parts: A1 A2
Area = A1 + A2 A1 A2 10 10 12
16-12 =4
Area = LW + 1/2 BH
Area = 10 x ½ x 4 x 10
Area =
Area = 140m2

16. What Goes In The Box ? Find the area of the shapes below : (1) 8cm
(2)
10.2 m
6.3m
32.13m2
(3)
25m
18m
12m
258m2

17. The Area Of A Parallelogram.
A Parallelogram is any closed shape which has two sets of parallel sides.

18. We are now going to find a formula for the area of a parallelogram:
Divide the shape into parts: h b
Area = b x h
Height and Base have to be perpendicular

19. Example 1
Calculate the area of the parallelogram below :
Solution ( Using the formula).
16cm
13cm
Area = b x h
b = 16
h =13
Area = 16 x 13
Area = 208 cm2