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Year 8 Mathematics Area and Perimeter
Area and Perimeter
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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
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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
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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
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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?
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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
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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
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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
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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
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