9'1 Areas of Rectangles and Parallelograms

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9.1 Areas of Rectangles and Parallelograms

• Geometry CP
• Chapter 9 Area

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Definition

• The area of a plan figure is the measure of the
  region enclosed by the figure

Your challenge is finding the number of squares
of unit length that fill the figure
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Definitions

• Base a side of a rectangle (or parallelogram)
• Altitude to the base a segment perpendicular to
  the base with one endpoint on the base and the
  other endpoint on the opposite side

Base
Altitude
Altitude
Base
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Area of a Rectangle

• C-81 Rectangle Area Conjuncture
• The area of a rectangle is given by the formula A
  b ? h, where
• A is the area
• b is the length of the base
• h is the height of the rectangle

any side
the side perpendicular to the base altitude
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Area of a Parallelogram

• C-82 Parallelogram Area Conjuncture
• The area of a parallelogram is given by the
  formula A b ? h, where
• A is the area
• b is the length of the base
• h is the height of the parallelogram

any side
the side perpendicular to the base altitude
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Examples

• Find the Area of the parallelogram

A b ? h
A 6m ? 2.5 m
A 15 m2
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Examples - you try first!

• Find the Area of the parallelogram

A b ? h
A 3m ? 3.5 m
A 10.5 m2
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Examples

• What is the area of the parallelogram?

8 yards
A b ? h
5 yards
A 8 yds ? 5 yds
14 yards
A 40 sq yds
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Examples

• Find the height of the parallelogram if the Area
  is 156 sq in.

A b ? h
h
17 in
156 sq in 12 in ? h
h 13 in
12 in
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Examples - you try first!

• What is the base of a parallelogram that has an
  area of 7.13 m2 and a height of 2.3m?

A b ? h
2.3 m
7.13 m2 b ? 2.3m
7.13 m2 b 2.3m
3.1 m b
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Homework

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