Areas of Parallelograms and Triangles

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Lesson 7.1 Areas of Parallelograms and Triangles
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height
base
Theorem 7.1 Area of a Rectangle
Area base x height or A bh
Is there another formula?
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height
width
base
length
Theorem 7.1 Area of a Rectangle
Area length x width or A lw
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Theorem 7.2
Areabase x height
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The base can be any side the height is a
segment perpendicular to that side
note the height can also be
called an altitude.
height
base
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The base can be any side the height is a
segment perpendicular to that side
height
base
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The base can be any side the height is a
segment perpendicular to that side
Sometimes you extend the base
height
base
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Just make sure that the height is perpendicular
to its corresponding side!
Sometimes you extend the base
height
base
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Rotate your paper to see the sideways ones!
height
base
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FIND THE AREA OF THIS SHAPE
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SOLUTION !
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Find the length of this height
2.
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3. A parallelogram has sides 15 cm and 18
cm. The height corresponding to the 15 cm base is
9 cm. Find the height corresponding to the 18 cm
base.
18
9
15
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4. For ABCD, find CF.
F
D
C
13 in
12 in
B
A
10 in
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5.Find the area of PQRS with vertices P(1,2),
Q(6,2), R(8,5), and S(3,5)
S
R
3 units
P
Q
5 units
Abh5(3) or 15 sq units
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The base of a triangle can be any of its 3 sides.
The height of the triangle is the length of the
altitude to the line containing the base.
height
base
base
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Theorem 7.3 Area of a Triangle The area of a
triangle is half the product of a base and the
corresponding height.
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6. Find the area of this triangle.
6.4 ft
10 ft
4ft
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7. Find the area of the triangle. 8. Find the
length of
5 cm
12 cm
13 cm
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7.Find the area of the triangle.
5 cm
12 cm
13 cm
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8.Find the length of
5 cm
12 cm
13 cm