8­1.notebook
February 04, 2013
Area
• Area:
• the measure of the region enclosed by the figure
• You can measure the area by counting the number of
square units that you can arrange to fill the figure
completely
8.1 Areas of Rectangles and
Parallelograms
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Area
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Base and Height
• To find the area of a rectangle you could simply
count the squares inside it
• Any side of a rectangle can be called a base. Then
the other side would be called the height.
• We need area formulas when we do not know how
many squares are inside the figure
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Area of a rectangle
• A=bh
• b:base
h:height
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Area of irregular shapes
• How can you use the area of a rectangle to find the
area of the shape below?
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8­1.notebook
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Find the Area:
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Parallelograms
• Just as a rectangle, any side of a parallelogram
can be called the base.
• However, the height of a parallelogram is usually
not a side.
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Parallelograms
• An altitude of a parallelogram is any segment from
one side of a parallelogram perpendicular to a line
through the opposite side
• The length of the altitude is called the height
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Altitude
• The altitude can be inside or outside the
parallelogram
• No matter where you draw the altitude to a base,
its height should be the same, because the opposite
sides are parallel
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8­1.notebook
February 04, 2013
Area of a Parallelogram
• A=bh
• b:base
h:height
Find the height
• Find the height of the parallelogram that has area
7.13 m2 and base length of 2.3 m.
• Find the area:
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Homework
• Page 425:1-15, 17, 23
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