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April 08, 2013
DO NOW
1. What type of quadrilateral has exactly one pair of parallel
sides?
Complete the statement using always, sometimes, or never.
2. A rhombus is __________ a parallelogram.
3. A square is _________ a trapezoid.
Mar 27­4:35 PM
10.3 Areas of Parallelograms and Trapezoids
The base of a parallelogram is the length of any one of its
sides. The height of a parallelogram is the perpendicular
distance between the side whose length is the base and the
opposite side.
Notice that the area is the product
of the base b and the height h.
Mar 27­4:41 PM
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April 08, 2013
The base of a parallelogram is 5 inches. The height is
twice the base. Find the area of the parallelogram.
Find the height.
Find the area.
Mar 27­4:45 PM
The height of a parallelogram is 12 inches. The
base is two thirds of the height. Find the area of
the parallelogram.
Mar 27­4:59 PM
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Trapezoids
The bases of a trapezoid are the lengths of its parallel
sides. The height of a trapezoid is the perpendicular
distance between the sides whose lengths are the bases.
The diagram shows how two congruent trapezoids with
height h and bases b1 and b2 can be put together to form
a parallelogram with base b1 and b2 and height h.
Mar 27­4:47 PM
Did you notice that the area of the large parallelogram
we just formed was twice the area of either trapezoid?
Mar 27­4:54 PM
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Draw a triangle.
Draw a dashed segment
parallel to its base.
If you were to cut along the
dashed line you would have a
trapezoid.
You could actually use the
formula for the area of a
trapezoid to find the area of a
triangle if you think of one of
its bases as being a point, with
no length.
Mar 27­5:17 PM
The diagram shows one of the
trapezoids in a quilt design.
Find the area of the trapezoid.
A=
1
(b1 + b2)h
2
Mar 27­4:56 PM
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Find the area of the trapezoid.
Mar 27­5:14 PM
Mar 27­5:25 PM
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Finding an unknown length
The height of a trapezoid is 6 meters. One of its bases is 8
meters. The area of the trapezoid is 54 square meters.
Find the other base.
A=
1 (b + b )h
2
2 1
Mar 27­5:30 PM
The bases of a trapezoid are 11 inches and 17 inches.
The area of the trapezoid is 56 square inches. Find
the height.
Mar 27­5:32 PM
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Acc. 10.3.notebook
April 08, 2013
Using area of trapezoids
You are building an L-shaped desktop
for your room. The dimensions of the
desktop are shown. Find the area of
the desktop.
Divide the desktop into two
trapezoids. Find the sum of the
areas of trapezoids A and B.
Could the desktop have been
divided in another way?
Mar 27­5:35 PM
A banner is made up of two
congruent trapezoids. Find the
area of the banner.
Mar 27­5:39 PM
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How do you find the area of a trapezoid?
Mar 27­5:40 PM
Puzzle
Six equilateral triangles are arranged to form a
regular hexagon. If each triangle has a perimeter of
6 centimeters, what is the perimeter of the regular
hexagon?
Hint: Draw a
picture.
Mar 27­5:41 PM
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Find the area of each figure.
Mar 27­5:20 PM
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