1. Area Learning Intentions
Calculate the area of a square, rectangle and triangle

2. Definition
Part of a two dimensional surface enclosed within a specified boundary or geometric figure

3. Finding an area
Area is described in terms of the number of unit squares that fit inside or cover a shape.
This is an area of 1 square unit
This is an area of 2 square units

4. Irregular shapes
The area of any shape can be found by counting the number of unit squares inside.
This shape has an area of 12 square units

5. Regular shapes
For many shapes there are formulae that help you count the square units.
Squares
Rectangles
Triangles
Circles
These include
Any there are many more

6. Area of a rectangle Here is a rectangle.
It can be covered with 6 square units
It has an area of 6 square units

7. Area of a rectangle
If the size of the rectangle is known the area can be calculated using the formula
Area = length x width

8. Here is another rectangle. This time the squares are not shown
Here is another rectangle. This time the squares are not shown. The area is found using the formula Area = Length x width

9. The area is 20 square units.
If the units are in
centimetres
then the area is 20 square
Centimetres, written as 20cm2
If the units are in metres
then the area is 20 m2

10. Questions for you to try
Make a note of your answers before you proceed.
Find the area of a rectangle of size 3 cm by 6 cm
Find the area of a rectangle 5 cm by 2 cm
Find the area of a rectangle 7 cm by 8 cm
Click to see answers

11. Answers
18 cm2
10 cm2
56 cm2
Find the area of a rectangle of size 3 cm by 6 cm
Find the area of a rectangle 5 cm by 2 cm
Find the area of a rectangle 7 cm by 8 cm

12. Area of a square If you were Ok with rectangles squares are easy
The rectangle area formula can be changed
Rectangle area formula = Length x width L
And becomes
Area of a square = Length x Length L

13. Area of a square Example 3 Find the area of a square with sides 3 3
Area = length x length

14. Area of a square Example Find the area of a square with sides 3
Area = length x length
Area is 9 square units

15. Questions for you to try
Make a not of your answers before you proceed.
Find the area of a square of size 6 cm by 6 cm
Find the area of a square 5 cm by 5 cm
Find the area of a square 7 cm by 7 cm
Click to see answers

16. Answers
36 cm2
25 cm2
49 cm2
Find the area of a square of size 6 cm by 6 cm
Find the area of a square 5 cm by 5 cm
Find the area of a square 7 cm by 7 cm

17. Area of a Triangle
These two triangles are identical

18. Area of a Triangle
These two triangles are identical

19. Area of a Triangle
These two triangles are identical

20. Area of a Triangle
These two triangles are identical

21. Area of a Triangle
These two triangles are identical

22. Area of a Triangle
These two triangles are identical

23. Area of a Triangle
These two triangles are identical

24. Area of a Triangle
These two triangles are identical

25. Area of a Triangle Together they make a rectangle.
The area of each triangle is half of the area of the rectangle.
This gives us a formula for
The area of a triangle.
Area = ½ Length X height
An alternative way of writing this is
Area = ½ base X height

26. Area of a Triangle Example Find the area of a triangle with base 4 cm
and height 5 cm 5
Area = ½ base X height 4
Area = ½ x4 x 5
Area = 10
cm2

27. Questions for you to try
Make a note of your answers before you proceed.
Find the area of a triangle of base 6 cm and height 6 cm
Find the area of a triangle of base 5 cm and height 5 cm
Find the area of a triangle of base 7 cm and height 7 cm
Click to proceed

28. Answers Find the area of a triangle of base 6 cm and height 6 cm