# Saturday, 30 September 2006 ©RSH Area Rectangles, Triangles and Composite Shapes.

## Presentation on theme: "Saturday, 30 September 2006 ©RSH Area Rectangles, Triangles and Composite Shapes."— Presentation transcript:

Saturday, 30 September 2006 ©RSH Area Rectangles, Triangles and Composite Shapes

Saturday, 30 September 2006 ©RSH Background Lots of people need to find the area of shapes –How many tins of paint to cover the walls –How many tiles to cover the roof –Fitting carpets –Area of lawns –Area of a football pitch –Area of a town –Fishing areas –Size of the building plot –Etc.

Saturday, 30 September 2006 ©RSH Triangles Area = ½ x base x height Triangles Area = ½ x base x height Notes Example Find the area of this triangle Example Find the area of this triangle Area = ½ x 6 x 3 = 9 cm²

Saturday, 30 September 2006 ©RSH Composite Shapes Split them up. Work out the area of each part. Add up the separate areas. Composite Shapes Split them up. Work out the area of each part. Add up the separate areas. Notes Area = 12 + 12 = 24 cm²

Saturday, 30 September 2006 ©RSH Composite Shapes Split them up. Work out the area of each part. Add up the separate areas. Composite Shapes Split them up. Work out the area of each part. Add up the separate areas. Notes Area = area of triangle + area of rectangle

Saturday, 30 September 2006 ©RSH Trapezium (quadrilateral with 2 parallel sides) Area = ½ x (a +b) x h Trapezium (quadrilateral with 2 parallel sides) Area = ½ x (a +b) x h Notes

Saturday, 30 September 2006 ©RSH Example Area = ½ x (a +b) x h Area = ½ x (8 + 10) x 6 = ½ x 18 x 6 = 9 x 6 = 54 cm ² Example Area = ½ x (a +b) x h Area = ½ x (8 + 10) x 6 = ½ x 18 x 6 = 9 x 6 = 54 cm ² Notes

Saturday, 30 September 2006 ©RSH Parallelogram (quadrilateral, opposite sides are parallel) Area = b x h Parallelogram (quadrilateral, opposite sides are parallel) Area = b x h Notes

Saturday, 30 September 2006 ©RSH Triangle Area = ½ x base x height Triangle Area = ½ x base x height Notes OR If you know the base and the height Triangle Area = ½ ab sin C Triangle Area = ½ ab sin C If you know two sides and the angle between them

Saturday, 30 September 2006 ©RSH Notes Triangle Area = ½ ab sin C Triangle Area = ½ ab sin C Example Area = ½ ab sin C = ½ x 6 x 7 x sin 50° = 16.1 cm² Example Area = ½ ab sin C = ½ x 6 x 7 x sin 50° = 16.1 cm²