10-3 Break into Simpler Parts
Warm Up
Problem of the Day
Lesson Presentation
Course 1

10-3 Break into Simpler Parts
Warm Up
1. What is the area of a rectangle with length 10 cm and width 4 cm?
40 cm 2
2. What is the area of a parallelogram with base 18 ft and height 12 ft?
216 ft 2
3. What is the area of a triangle with base
16 cm and height 8 cm?
64 cm 2
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10-3 Break into Simpler Parts
Problem of the Day
Four squares are stacked in a tower.
The bottom square is 12 inches on a side. The perimeter of each of the other squares is half of the one below it. What is the perimeter of the combined figure?
69 in.
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10-3 Break into Simpler Parts
.
Course 1

10-3 Break into Simpler Parts
Additional Example 1A: Finding Areas of
Composite Figures
Find the area of the polygon.
1.7 cm
A.
4.9 cm
2.1 cm
1.3 cm
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Think: Break the polygon apart into rectangles.
Find the area of each rectangle.

10-3 Break into Simpler Parts
Additional Example 1A Continued
1.7 cm
4.9 cm
2.1 cm
1.3 cm
A = l w
A = 4.9
•
1.7
A = 8.33
A = l w
A = 2.1
•
1.3
A = 2.73
Write the formula for the area of a rectangle.
8.33 + 2.73 = 11.06
Add to find the total area.
The area of the polygon is 11.06 cm 2 .
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10-3 Break into Simpler Parts
Additional Example 1B Continued
Find the area of the polygon.
B.
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Think: Break the figure apart into a rectangle and a triangle.
Find the area of each polygon.

10-3 Break into Simpler Parts
Additional Example 1B Continued
A = l w
A =
2 b h
A = 28
•
24 A = 28
•
12
A = 672
A = 168
672 + 168 = 840
Add to find the total area of the polygon.
The area of the polygon is 840 ft 2 .
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10-3 Break into Simpler Parts
Try This: Example 1A
Find the area of the polygon.
1.9 cm
A.
5.5 cm 1.5 cm
2 cm
3.4 cm
1.9 cm
5.5 cm
Think: Break the polygon apart into rectangles.
Find the area of each rectangle.
2 cm
1.5 cm
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10-3 Break into Simpler Parts
Try This: Example 1A Continued
1.9 cm
5.5 cm
2 cm
1.5 cm
A = l w
A = 5.5
•
1.9
A = 10.45
A = l w
A = 2
•
1.5
A = 3
Write the formula for the area of a rectangle.
10.45 + 3 = 13.45
Add to find the total area.
The area of the polygon is 13.45 cm 2 .
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10-3 Break into Simpler Parts
Try This: Example 1B
Find the area of the polygon.
B.
20 ft
36 ft
16 ft
22 ft
22 ft
20 ft
22 ft
Think: Break the figure apart into a rectangle and a triangle.
Find the area of each polygon.
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10-3 Break into Simpler Parts
Try This: Example 1B Continued
20 ft
16 ft
22 ft
22 ft
A = l w
A =
2 b h
A = 22
•
20 A = 22
•
16
A = 440
A = 176
440 + 176 = 616
Add to find the total area of the polygon.
The area of the polygon is 616 ft 2 .
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10-3 Break into Simpler Parts
Additional Example 2: Art Application
Patrick made a design. All the sides are 5 inches long, except for two longer sides that are each 20 inches. All the angles are right angles. What is the area of the quilt design?
20 in.
5 in.
20 in.
Think: Divide the design into 3 rectangles. Find the area of one rectangle that has a length of 20 in and a width of 5 in.
A = l w Write the formula.
A = 20
•
5 = 100
3
•
100 = 300
Multiply to find the area of the 3 rectangles.
The area of the design is 300 in 2 .
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10-3 Break into Simpler Parts
Helpful Hint
You can also use the formula A = s 2 , where s is the length of a side, to find the area of a square.
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10-3 Break into Simpler Parts
Try This: Example 2
Yvonne made quilt design. All the sides are 4 inches long, except for the two longer sides that are each
16 inches. All the angles are right angles. What is the area of the quilt design?
4 in.
16 in.
Think: Divide the quilt design into
10 squares. Find the area of one square that has a side length of 4 in.
16 in.
A = l w
Write the formula.
A = 4
•
4 = 16
10
•
16 = 160
Multiply to find the area of the
10 squares.
The area of the quilt design is 160 in 2 .
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10-3
Lesson Quiz
Find the area of the figure shown.
220 units 2
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