2. Main Idea and New Vocabulary Key Concept: Area Formulas
Example 1: Find the Area of a Composite Figure
Example 2: Real-World Example
Example 3: Find the Area of a Shaded Region
Lesson Menu

3. Find the area of composite figures.
Main Idea/Vocabulary

4. Key Concept

5. Find the Area of a Composite Figure
Find the area of the composite figure. Round to the nearest tenth.
This area can be separated into a rectangle and a semicircle.
Example 1

6. Find the Area of a Composite Figure
Area of a rectangle
Area of a semicircle
A = bh
A = 12 • 6
A = 72
Example 1

7. Find the Area of a Composite Figure
Answer: The area of the figure is about or 86.1 square centimeters.
Example 1

8. Find the area of the composite figure. Round to the nearest tenth.
A in2
B in2
C in2
D in2
Example 1 CYP

9. DOG HOUSE One side of a dog house is composed of a square and a triangle. How much wood is needed for this side of the dog house to the nearest tenth of a square foot?
The sides of the square measure 2.5 feet. The base of the triangle is 2.5 feet and the height is 4 – 2.5 or 1.5 feet.
Example 2

10. Area of a square Area of a triangle A = s2 A = 2.52 A = 6.25
The total area is or
Answer: So, about 8.1 square feet of wood is needed for this side of the dog house.
Example 2

11. SIDEWALK A patio is composed of a trapezoid and a rectangle
SIDEWALK A patio is composed of a trapezoid and a rectangle. What is the area of the patio?
A. 20 ft2
B. 56 ft2
C. 60 ft2
D. 76 ft2
Example 2 CYP

12. Find the Area of a Shaded Region
In the figure below, two congruent triangles are cut from a rectangle. Find the area of the shaded region. Round to the nearest tenth if necessary.
Find the area of the rectangle and subtract the area of the two triangles.
Example 3

13. Find the Area of a Shaded Region
Area of a rectangle
A = bh
A = 16 • 12 b = 16, h = 12
A = 192 Simplify.
Example 3

14. Find the Area of a Shaded Region
Area of a triangle
b = 8, h = 6
Simplify.
Answer: The area of the shaded region is – 48 or 144 square inches.
Example 3

15. Two triangles are cut from a square. Find the area of the shaded region. Round to the nearest tenth if necessary.
A. 80 cm2
B. 90 cm2
C. 100 cm2
D. 110 cm2
Example 3 CYP