Area of a rectangle

1
Simple Areas
Area of a rectangle
Area of a right-angled triangle
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Area of composite shapes
2
Starter Questions
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34o
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Area of a Rectangle
Learning Intention
Success Criteria

1. To be able to state area formula for a rectangle.

1. To come up with a formula for the
area of a rectangle.

• Apply formula correctly.
• (showing working)

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1. Use the formula to solve problems.

• Answer containing
• appropriate units

4

Problem
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Only 5 a square metre!
How much for this one?
?
5
Problem
1m
1m
1 square metre
6 m
6 square metres
6 square metres
3 m
6 square metres
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3 rows of 6 squares
3 x 6
18 square metres
18 x 5 90
How much for 18 square metres?
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Area of a rectangle
6
6 m
length
3
3 m
breadth
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6
x 3
18 m²
Area
length
x breadth
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Example 1
Area length x breadth
A l x b
11 cm
A 11 x 6
6 cm
A 66 cm²
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Find the area of the rectangle
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Example 2
Area length x breadth
A l x b
A 12 x 12
A 144 cm²
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12 cm
Find the area of the square
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Starter Questions
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123o
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Area of A Right-Angled Triangle
Learning Intention
Success Criteria

1. Know area of a right-angled triangle formula

1. Use the area of a rectangle formula to help
us to come up with a formula to calculate the
area of any right-angled triangle.
2. Use formula to work out area of triangle.
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3. Show all working and units.
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Area of a right-angled triangle
4 cm
7 cm
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Area of rectangle
l x b
28 cm²
7 x 4
Area of triangle
½ x Area of rectangle
½ x 28
14 cm²
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Area of triangle Short cut
4 cm
height
base
7 cm
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Area of triangle
½ x 7 x 4
14 cm²
½ x 28
Area ?
x base
x height
½
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Example 1
Area ?½ x base x height
A? ½ x b x h
A? ½ x 15 x 10
10 cm
A? 75 cm²
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15 cm
Find the area of the triangle
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Example 2
Area ?½ x base x height
8 cm
A? ½ x b x h
A? ½ x 8 x 12
12 cm
A? 48 cm²
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Find the area of the triangle
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Area of a right-angled triangle
Now try worksheet Exercise 1
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Starter Questions
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Area of a Composite
Made up of Simple shapes
Learning Intention
Success Criteria

1. To be able to use knowledge gained so far to find
   the area of more complicated shapes..

1. To use knowledge to find area of more
complicate shapes.
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1. Show appropriate working.

18
Composite shapes
10 cm
6 cm
?
3 cm
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Composite shapes
10 cm
6 cm
(1)
6 cm
(2)
?
3 cm
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Area (1)
l x b
60 cm²
10 x 6
Area (2)
½ x b x h
½ x 3 x 6
9 cm²
Area of shape
(1) (2)
69 cm²
60 9
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Example 1
l x b
Area (1)
15 x 8
120 cm²
?
8cm
(1)
Area (2) l x b
9 x 3
27 cm²
(2)
(1) (2)
Area of shape
120 27
9cm
147 cm²
Find the area of the shape
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Example 2
l x b
Area (1)
20 x 12
240 cm²
Area (2) l x b
10 x 6
(2)
60 cm²
(1) (2)
Area of shape
240 -60
(1)
180 cm²
Find the area of the shape
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Composite shapes
Now try worksheet Exercise 2
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