1. Area & Perimeter Learning Objectives: 1.Learn to find perimeter and area of simple & compound/composite shapes. 2.Practice solving problems involving area and perimeter. 3.Review Percentages, Fractions and Decimals Keywords: Perimeter, Area, Parallelogram, Trapezium, Perpendicular 15/03/2011

2. Area of a rectangle Width Length Area of a rectangle = length x width

3. Area of a Parallelogram A parallelogram has an area equal to a rectangle with the same base and height measurements: Therefore: Area of a parallelogram = base × (perpendicular) height.

4. Example Find the area of this parallelogram- Solution: To find the area, we need two measurements that are perpendicular to each other. Here we see that the base is 6.8 cm and the height is 4.3 cm. So area = 6.8 × 4.3 = 29.24 cm 2.

5. Area of a Triangle A triangle has an area that is half the area of the surrounding rectangle: So: Area of a triangle = ½ × base × height or area =

6. Example Find the area of the triangle shown: Solution: Area =

7. Area of a Trapezium The formula for finding the area of a trapezium is: Area = In this formula, a and b represent the lengths of the parallel sides and h represents the height of the trapezium. Instead of using the formula, some people prefer to remember the steps involved in finding the area of a trapezium: Step 1: Add together the parallel sides Step 2: Multiply by the height Step 3: Divide by 2. a b h

8. Solution: Using the formula: So: (working out the value of the brackets) So: Example Find the area of the trapezium shown below: or using the steps: Step 1: Add together the parallels sides 13 + 17 = 30 Step 2: Multiply by the height: 30 × 6.5 = 195 Step 3: Divide by 2: 195 ÷ 2 = 97.5 cm 2.

9. Plenary Work in pairs of groups of 3: Q1 2 squares are joined together to form a rectangle. The area of the rectangle is 72cm 2. Find the area of each square and the perimeter of the rectangle. Q2 3 triangles are joined to form a compound shape which is made up of a square with a triangle on top. The area of triangle is 8cm 2. Find the perimeter of the compound shape. Q3 A square is cut from a larger square. The area of smaller square is 9cm 2. The ratio of length smaller square to larger square is 4 : 1. Find the area of larger square before it was cut from.