10-3 Break into Simpler Parts
Course 1
Warm UpWarm Up
Lesson PresentationLesson Presentation
Problem of the DayProblem of the Day
Warm Up
1. What is the area of a rectangle with length 10 cm and width 4 cm?
2. What is the area of a parallelogram with base 18 ft and height 12 ft?
3. What is the area of a triangle with base 16 cm and height 8 cm?
40 cm2
216 ft2
64 cm2
Course 1
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.
Course 1
10-3 Break into Simpler Parts
Today’s Learning Goal Assignment
Learn to break a polygon into simpler parts to find its area.
Course 1
10-3 Break into Simpler Parts
Additional Example 1A: Finding Areas of Composite Figures
Find the area of the polygon.
A.
Think: Break the polygon apart into rectangles.
Find the area of each rectangle.
1.7 cm
4.9 cm 1.3 cm
2.1 cm
Course 1
10-3 Break into Simpler Parts
Additional Example 1A Continued
A = lw A = lw
A = 4.9 • 1.7 A = 2.1 • 1.3Write the formula for the area of a rectangle.A = 8.33 A = 2.73
8.33 + 2.73 = 11.06 Add to find the total area.
The area of the polygon is 11.06 cm2.
1.7 cm
4.9 cm
1.3 cm
2.1 cm
Course 1
10-3 Break into Simpler Parts
Additional Example 1B Continued
Find the area of the polygon.
B.
Think: Break the figure apart into a rectangle and a triangle.
Find the area of each polygon.Course 1
10-3 Break into Simpler Parts
Additional Example 1B Continued
A = lw
A = 28 • 24
A = 672 A = 168
672 + 168 = 840 Add to find the total area of the polygon.
The area of the polygon is 840 ft2.
A = bh12__
A = 28 • 1212__
Course 1
10-3 Break into Simpler Parts
Try This: Example 1A
Find the area of the polygon.
A.
Think: Break the polygon apart into rectangles.
Find the area of each rectangle.
1.9 cm
5.5 cm 1.5 cm 2 cm
1.9 cm
1.5 cm
2 cm
3.4 cm
5.5 cm
Course 1
10-3 Break into Simpler Parts
A = lw A = lw
A = 5.5 • 1.9 A = 2 • 1.5Write the formula for the area of a rectangle.A = 10.45 A = 3
10.45 + 3 = 13.45 Add to find the total area.
The area of the polygon is 13.45 cm2.
Try This: Example 1A Continued
1.9 cm
5.5 cm 1.5 cm 2 cm
Course 1
10-3 Break into Simpler Parts
Try This: Example 1B
Find the area of the polygon.
B.
Think: Break the figure apart into a rectangle and a triangle.
Find the area of each polygon.
36 ft
22 ft
20 ft
20 ft
22 ft
22 ft
16 ft
Course 1
10-3 Break into Simpler Parts
A = lw
A = 22 • 20
A = 440 A = 176
440 + 176 = 616 Add to find the total area of the polygon.
The area of the polygon is 616 ft2.
A = bh12__
A = 22 • 1612__
Try This: Example 1B Continued
20 ft22 ft
22 ft
16 ft
Course 1
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?
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.Write the formula.A = lw
A = 20 • 5 = 100
3 • 100 = 300 Multiply to find the area of the 3 rectangles.
The area of the design is 300 in2.
20 in.
20 in.
5 in.
Course 1
10-3 Break into Simpler Parts
You can also use the formula A = s2 , where s is the length of a side, to find the area of a square.
Helpful Hint
Course 1
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?
Think: Divide the quilt design into 10 squares. Find the area of one square that has a side length of 4 in.
Write the formula.A = lw
A = 4 • 4 = 16
10 • 16 = 160Multiply to find the area of the 10 squares.
The area of the quilt design is 160 in2.
4 in.16 in.
16 in.
Course 1
10-3 Break into Simpler Parts
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