Y8MA3G_Perimeter and Area Compound Shapes_12_01_2012

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Perimeter & Area of compound shapes : 

Perimeter & Area of compound shapes Lesson objective: To be able: to calculate the perimeter and the area of compound shapes. [Level 5] Key words: compound shapes Starter: For the following, draw the shapes in your books and find the perimeter and area. A square with sides 2cm A rectangle with sides 5cm and 4cm A square with sides 6cm

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How to multiply with decimals Combine Algebra with Geometry… Example : 8 x 0.2 Ignore decimal points 8x2 =16 Count decimal places =1 1.6 Example: 1.2 x 0.8

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9 m 4.2 m P = ? A = ? P = 2x9 + 2x4.2 = = 18 + 8.4 P = 26.4 m A = 9x4.2= A = 37.8 m² Example…

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Work in pairs… Find the AREA of each of the following rectangles. Remember to use the correct units.

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Example of compound shapes… 6 cm 4 cm 4 cm 10 cm P = ? A = ?

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Can you find the perimeter and the area for these shapes ?? 5 cm 2 cm 4 cm 5 cm 4 cm 2 cm 9 cm 8 cm 3 cm 6 cm 2 cm Work in pairs… 4 cm 4 cm 4 cm 4 cm 3 cm 3 cm 12 cm 12 cm

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5 cm 2 cm 4 cm 5 cm 4 cm 2 cm 9 cm

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8 cm 3 cm 6 cm 2 cm

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4 cm 4 cm 4 cm 4 cm 3 cm 12 cm

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Plenary… 12 cm 4 cm 5 cm 9 cm Uncle Max finds the area of this compound shape Explain why he is wrong. Calculate the correct answer. Area = 4 x 5 + 9 x 12 = 20 + 108 = 80cm2