# Document 174262

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**Derive and
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use the formula for the area of a right triangle and of a
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parallelogram by comparing it with the area of a rectangle (i.e., two of
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the same triangles make a parallelogram with twice the area; a
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UNDERLYING SKILLS AND CONCEPTS:
find area of rectangles;
find area of right triangles
parallelogram is compared with a rectangle of the same area found by
cutting and pasting a right triangle on the parallelogram).
Find the Area of Parallelograms
You can use what you know about
the area of rectangles to find the area
of a parallelogram.
Area of rectangles
is very useful!
7
12
Cut the parallelogram.
Move one piece to make a rectangle.
h
b
Very Important:
The height of a figure is
always measured perpendicular
to the base of the figure.
12
The length of the base is still 12 units.
The height is still 7 units.
Now you can find the area of the rectangle.
A!b"h
A ! 12 " 7
A ! 84
The area of the rectangle is 84 square units.
You made the rectangle from the
parallelogram. So, the area of the parallelogram
is also 84 square units.
The formula for the area of a parallelogram:
A!b"h
page 316
E x am p l E
Find the area of the parallelogram.
5 in.
b ! 6 in.
The height is 5 inches.
The base is 6 inches.
A!b"h
A!6"5
A ! 30 in.2
The area is 30 square inches.
Chapter 27 – Lesson 2
7
Name
P RAC T I C E
Find the area of each parallelogram.
1.
2.
3.
2 cm
5.5 m
b 7 cm
4 ft
b6m
b 3 ft
14 cm2
12 ft2
4.
5.
33 m2
6.
5 mm
9 in.
6 yd
3 mm
5 yd
6 in.
54 in.2
7. b 8 in.
h 6 in.
30 yd2
15 mm2
8. b 12 ft
9. b 15 mm
10. b 20 cm
108 ft2
150 mm2
320 cm2
h 9 ft
48 in.2
11. Which expression can you use to find
the area of a parallelogram that has a
base of 12.5 units and a height of
3.25 units?
Math
Reasoning
h 10 mm
A
B
C
D
h 16 cm
12.5 3.25
12.5 3.25
12.5 3.25
12.5 3.25
Area Algebra
MR2.2
12. A parallelogram has a base of 10 cm and an area of 50 cm2.
What is its height? Explain how you decided.
5 cm I know that base height area.
I know that base is 10 cm and the area is 50 cm2.
So, I can find 10 some number 50.
I can use inverse operations or mental math.
50 10 5. So, the height is 5 centimeters.
Chapter 27 – Lesson 2
page 317
MCX94.HW.CL.G5.FM&Lesson.v211
8/2/04
18:03
Page 212
Name
…at home!
P RAC T I C E
Find the area of each parallelogram.
2.
1.
3.
2 cm
5.5 m
b 8 cm
5 ft
b7m
b 3 ft
16 cm2
5.
38.5 m2
6.
6 mm
12 yd
8 in.
4 mm
10 yd
6 in.
48 in.2
120 yd2
24 mm2
7. b 16 in.
8. b 18 ft
9. b 30 mm
160 in.2
216 ft2
600 mm2
h 10 in.
h 12 ft
11. Which expression can you use to
find the area of a parallelogram that
has a base of 14.5 units and a height
of 6.25 units?
Math
Reasoning
h 20 mm
A
B
C
D
10. b 40 cm
h 32 cm
1,280 cm2
14.5 6.25
14.5 6.25
14.5 6.25
14.5 6.25
Area Algebra
MR2.2
12. A parallelogram has a base of 25 cm and an area of 75 cm2.
What is its height? Explain how you decided.
I know that base height area.
I know that base is 25 cm and the area is 75 cm2
So, I can find 25 some number 75.
I can use inverse operations or mental math.
75 25 3. So, the height is 3 centimeters.
page 212
Home Resource and Homework
Chapter 27 Lesson 2
4.
15 ft2
MCX94TEG5CH01_32.v7.4.2 2/24/01 19:50 Page 583
Name
P RAC T I C E
Find the area of each parallelogram.
1.
2.
3.
2 cm
5.5 m
b 7 cm
4 ft
b6m
b 3 ft
14 cm2
12 ft2
4.
5.
33 m2
6.
5 mm
9 in.
6 yd
3 mm
5 yd
6 in.
54 in.2
7. b 8 in.
h 6 in.
30 yd2
15 mm2
8. b 12 ft
9. b 15 mm
10. b 20 cm
108 ft2
150 mm2
320 cm2
h 9 ft
48 in.2
11. Which expression can you use to find
the area of a parallelogram that has a
base of 12.5 units and a height of
3.25 units?
Math
Reasoning
h 10 mm
A
B
C
D
h 16 cm
12.5 3.25
12.5 3.25
12.5 3.25
12.5 3.25
Area Algebra
MR2.2
12. A parallelogram has a base of 10 cm and an area of 50 cm2.
What is its height? Explain how you decided.
5 cm I know that base height area.
I know that base is 10 cm and the area is 50 cm2.
So, I can find 10 some number 50.
I can use inverse operations or mental math.
50 10 5. So, the height is 5 centimeters.
Chapter 27 – Lesson 2
Student Book Page
page 317
Name
…at home!
P RAC T I C E
Find the area of each parallelogram.
2.
1.
3.
2 cm
5.5 m
b 8 cm
5 ft
b7m
b 3 ft
16 cm2
5.
38.5 m2
6.
6 mm
12 yd
8 in.
4 mm
10 yd
6 in.
48 in.2
120 yd2
24 mm2
7. b 16 in.
8. b 18 ft
9. b 30 mm
160 in.2
216 ft2
600 mm2
h 10 in.
h 12 ft
11. Which expression can you use to
find the area of a parallelogram that
has a base of 14.5 units and a height
of 6.25 units?
Math
Reasoning
h 20 mm
A
B
C
D
10. b 40 cm
h 32 cm
1,280 cm2
14.5 6.25
14.5 6.25
14.5 6.25
14.5 6.25
Area Algebra
MR2.2
12. A parallelogram has a base of 25 cm and an area of 75 cm2.
What is its height? Explain how you decided.
I know that base height area.
I know that base is 25 cm and the area is 75 cm2
So, I can find 25 some number 75.
I can use inverse operations or mental math.
75 25 3. So, the height is 3 centimeters.
page 212
Home Resource and Homework
Chapter 27 Lesson 2
4.
15 ft2
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