Chapter 7 Area

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Chapter 7Area

• Sec. 7 1
• Area of //-ogram and ?s

Objectives 1) To find the area of a
//-ogram. 2) To find the area of a ?.
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re-attach here
Cut here
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Area of parallelograms
Height The altitude of the
//-ogram. Line from a vertex of the
//-ogram ? to the opposite side.
Base Is any of its sides.
A bh
Area of a //-ogram units 2
Height
Base
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Example 1 Find the area of the following
//-ogram.
12m
10.5m
8m
A bh (12m)(8m) 96m2
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Example 2 Find the length of the other height
of the //-ogram.
A bh (15in)(9in) 135in2
9in
18in
A bh 135in2 (18in)x x 7.5in
15in
x
Which base corresponds to which height??
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A diagonal divides any //-gram into two ? ?s.
A
B
?ABD ? ?CBD
C
D
Area of a ?
A ½ bh
Height of ? Must be ? to base
Base of ?
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Example 3 Find the area of the following ?.
A ½ bh ½ (30cm)(13cm) 195cm2
31cm
13cm
30cm
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Example 4 Find the area of the following ? .
A ½ bh ½ (12ft)(5ft) 30ft2
13ft
5ft
12ft
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Ex5 Find the area shaded in yellow.
AY A1 A2 40in2 16in2 24in2
A ½bh ½(10in)(8in) 40in2
A ½bh ½(4in)(8in) 16in2
-1-
8in
2
6in
10in
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What have we learned????

• Area of a //-ogram
• Base and height must be ?

A bh

• Area of a ?
• - Base and height must be ?

A ½ bh
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extra - not part of lesson
AREA OF A TRAPEZOID
Hi. Lets derive the formula for the area for a
trapezoid.
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AREA OF A TRAPEZOID
h
Remember, there are two different bases on a
trapezoid.
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AREA OF A TRAPEZOID
First divide the trapezoid horizontally so the
height is divided in two.
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AREA OF A TRAPEZOID
?
Remember, we divided the height in two. Now,
rotate
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AREA OF A TRAPEZOID
?
?
until, you have a parallelogram.
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?
?
How would you represent the base of the
parallelogram?
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AREA OF A TRAPEZOID
Remember, we divided the height in two.
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AREA OF A TRAPEZOID
The area of this trapezoid is the same as the
parallelogram.What is the formula for area of a
trapezoid?
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