1. Year 8 Mathematics Area and Perimeter
Area and Perimeter

2. Learning Intentions Learning Intentions
Understand the terms Perimeter and Area
Understand that perimeter is a linear measure and is given in mm, cm, m, etc
Understand that area is a square measure and is given in mm2, cm2, m2, etc
Calculate the perimeters and areas of squares, rectangles and compound shapes
Convert between different metric units

3. Perimeter
The perimeter of a shape is the total distance around the outside of the shape
We measure the distance using mm, cm, m, km, etc.
When adding the distances the units must be the same.
Example:
Calculate the perimeter of this shape:
8 cm
20 mm

4. Compound Shapes A compound shape is made up from rectangles
To find the perimeter of compound shapes we add the lengths of all the sides
Sometimes the lengths of sides will be left out
Example: Find the perimeter of this shape:
Start by putting an asterisk in one corner
2 cm
8 cm
3 cm

5. Area
The area of a shape is a measure of the space contained within its perimeter
Area is measured in mm2, cm2, m2, km2, etc
To calculate area we can divide a shape up into squares and count the squares
Example:
Find the area of this leaf
Each square is 1 cm2
What squares do you count?

6. Area of Rectangles
The area of a rectangle is calculated by multiplying its length by its width
Example:
Find the area of this rectangle
7 cm
5 cm

7. Area of Compound Shapes
To find the area of a compound shape, we divide the shape up into rectangles
The area of the compound shape is the sum of the areas of the rectangles
Example:
Find the area of this shape
2 cm
8 cm
3 cm

8. Areas of Compound Shapes
Find the area of the shaded region
First find the area of the green rectangle
Then find the area of the white compound shape
Finally subtract the white area from the green
12cm
10cm
7cm
3cm
5cm
2cm

9. Converting between Units
Remember
1 km = 1000 m
1 m = 100 cm
1 cm = 10 mm
Change the following:
1.4 km = _____________ m
3.5 m = _____________ cm
10.4 cm = _____________ mm
235 mm = _____________ m
cm = _____________ km