1. © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.ukwww.brain-cells.co.uk Area of Parallelogram Level 6 Objectives: Calculate the areas parallelograms Understand how the formula can be obtained

2. © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.ukwww.brain-cells.co.uk 4 cm 5 cm 20 square centimetres is written as 20 cm 2 We can see that the area is 20 cm 2 Recap of Area Area is measured by the number of squares of a certain size needed to cover the shape. We could, for example, find the area of this rectangle by covering it with one centimetre squares.

3. © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.ukwww.brain-cells.co.uk 4 cm 5 cm Recap of Area Area = Base x Height The area can be found by multiplying the base by the height A = 5 x 4 A = 20 cm We can see that this is the correct answer

4. © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.ukwww.brain-cells.co.uk Area of a Parallelogram If we put a cm 2 grid onto a parallelogram there are incomplete squares and it is not so easy to see a formula for the area. We can, however, find a formula by doing this… 6 cm 4 cm

5. © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.ukwww.brain-cells.co.uk Area of a Parallelogram Cut off the end like this Put the onto the opposite end like this 6 cm 4 cm We have changed the parallelogram into a rectangle

6. © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.ukwww.brain-cells.co.uk Area of a Parallelogram Area = Base x Height A = 6 x 4 6 cm 4 cm A = 24 cm 2 So to find the area, we multiply the base by the height

7. © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.ukwww.brain-cells.co.uk We can now use the formula to calculate the area of any parallelogram. But we do need to take care that we use the vertical height not the length of the slope. 7.5 cm 5.3 cm 6.4 cm Area = Base x Height A = 7.5 x 5.3 A = 39.75 cm 2 Calculate the area of this parallelogram

8. © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.ukwww.brain-cells.co.uk 7.3 cm 6.2 cm 9.2 cm 6.7 cm 8.3 cm 9.5 cm 7.5 cm 5.3 cm Area = Base x Height A = 7.5 x 5.3 A = 39.75 cm 2 Calculate the area of this parallelogram Using the example as a guide, calculate the areas of these parallelograms 1. 2. 3. 45.26 cm 2 61.64 cm 2 78.85 cm 2

9. © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.ukwww.brain-cells.co.uk The Formula for a Parallelogram’s Area The next exercise can be copied from the screen but it is best done on the sheet that can be obtained from www.brain-cells.co.uk A copy is shown on the right.

10. © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.ukwww.brain-cells.co.uk Area of a Parallelogram - Review A review sheet covering this presentation is available from www.brain-cells.co.uk