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Basic Geometric Properties. Unit 3 Lesson 7 Finding Area of Figures made up of Triangles and Parallelograms. height. base. Reminders. Rectangle. length. Triangle. width. Area = length width. Area = ½ base height. Composite shapes.
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Basic Geometric Properties Unit 3 Lesson 7 Finding Area of Figures made up of Triangles and Parallelograms
height base Reminders Rectangle length Triangle width Area = length width Area = ½ base height
Composite shapes This is a composite shape because it is made up of more than one basic shape or
5 cm 8 cm 3 cm 12 cm Can you see why it is x = 7 cm? Example 1: Find the area of this shape We can split it into 2 rectangles, A and B x 40 cm2 A 21 cm2 B Rectangle A has area 5 8 = 40 cm2 For rectangle B, we have to find another length. Rectangle B has area 7 3 = 21 cm2 So total area = 40 + 21 = 61 cm2
Need to split up 4cm y 11cm x 5 cm Area x = 8 X 11 = Area y = 5 X 4 = 8 cm Total Area =
y 3cm x 10cm 4 cm 7 cm Area x = Area y = Total Area =
12 cm 6 cm 7 cm 5 cm 3 cm X Find the area We can split it into 3 rectangles, A, B and C C y 12cm2 A B 21cm2 21cm2 Because of the symmetry of the shape, can you see why these two lengths must be 3 cm each? Rectangle A Area = Can you also see why the dotted lines are y = 2 cm each Rectangle B Rectangle C Area = Total area =
You Try 3cm 1. 2. 6cm2 2cm 3cm 12cm2 9cm 7cm 4cm 6cm 5cm 3. 4. 4cm 7cm 2cm 8cm2 6cm 4cm 6cm 3cm 12cm2 7cm
8 cm 7cm y 4 cm x 9cm Area x = Area y = Total Area = 8 cm
Area of Compound Shapes 13 cm y 3cm Steps to success Split into small rectangles Calculate any missing lengths Work out area of each rectangle Add for total area Remember units (square!) 8cm x ? 4cm 9 cm Area x = 8 X 9 = 72 cm2 Area y = 3 X 4 = 12cm2 Total Area = 72 + 12 = 84 cm2
Other Compound Shapes Area x = 10 X 8 = 80 cm2 Area y = ½ X 8 X 4= 16 cm2 4 cm Total Area = 80 + 16 = 96cm2 y 14cm 10 cm x 8 cm
6 in 4 in 5 in 12 in Area of Composite Shapes Find the area of all three triangles. Plan: Area of a Triangle ½(b)(h) ½(6)(4) ½(24) One triangle is 12 square inches Since 3 triangles are the same. 3 x 12 = 36 square inches
6. Find the area and perimeter Area = 3 m 12.5 m 7.5 m 13 m
Find the area of the arrow. Area =
Find the area of the green only 10m 7m 1m 3m Big Area = 3 X 10 = 30m2 Green Area = 30 – 7 = 23m2 White Area = 7 X 1 = 7m2
Practice Problems pages 110 and 111 Odd #1 - 13 Your Choice Lesson is work on your pathway in Study Island