1. The document provides examples of calculating the areas of various shapes, including circles, rectangles, triangles, trapezoids, parallelograms, and composite figures. 2. It gives the formulas for calculating the areas of these shapes and shows step-by-step workings for multi-part composite figures and shaded regions. 3. The examples are meant to demonstrate how measurements can be used to describe real-world objects and areas.

1. Find the area of each circle. Round to the nearest tenth. Use 3.14
or for .
1. 2.
3. 4.
5. Rick wants to make a big cookie cake. If he uses a round cookie
sheet that is 12 inches in diameter, about how much cookie dough
will he need to cover the pan?
22
7
Course 2, Lesson 8-3


2. Course 2, Lesson 8-3
ANSWERS
1. 78.5 cm2
2. 314 m2
3. 28.3 in2
4. 50.2 ft2
5. 113 in²

3. Geometry
Course 2, Lesson 8-3
HOW do measurements help you
describe real-world objects?

4. Course 2, Lesson 8-3 Common Core State Standards © Copyright 2010. National Governors Association Center for Best Practices and Council
of Chief State School Officers. All rights reserved.
Geometry
• 7.G.4
Know the formulas for the area and circumference of a circle and
use them to solve problems; give an informal derivation of the
relationship between the circumference and area of a circle.
• 7.G.6
Solve real-world and mathematical problems involving area,
volume and surface area of two- and three-dimensional objects
composed of triangles, quadrilaterals, polygons, cubes, and right
prisms.

5. Course 2, Lesson 8-3 Common Core State Standards © Copyright 2010. National Governors Association Center for Best Practices and
Council of Chief State School Officers. All rights reserved.
Geometry
Mathematical Practices
1 Make sense of problems and persevere in solving them.
2 Reason abstractly and quantitatively.
3 Construct viable arguments and critique the reasoning of others.
4 Model with mathematics.

6. • To find the area of a composite
figure
• To find the area of a shaded
region
Course 2, Lesson 8-3
Geometry

7. Course 2, Lesson 8-3
Geometry
• composite figure

8. 1
Need Another Example?
2
3
4
Step-by-Step Example
1. Find the area of the
composite figure.
The figure can be separated into
a semicircle and a triangle.
Area of semicircle
The area of the figure is about 14.1 + 33 or 47.1
square meters.
Area of triangle
A = πr2
A ≈ • 3.14 • 32
A ≈ 14.1
A = bh
A ≈ • 11 • 6
A ≈ 33

9. Answer
Need Another Example?
Find the area of the composite figure. Round to
the nearest tenth.
86.1 cm2

10. 1
Need Another Example?
2
3
Step-by-Step Example
2. A miniature golf hole is
composed of a trapezoid
and a parallelogram. How
many square feet of turf
does the hole cover?
Area of trapezoid
So, 7.5 + 15 or 22.5 square feet of turf will be needed.
Area of parallelogram
A = h(b1 + b2)
A = (3)(2 + 3)
A = 7.5
A = bh
A = 6 • 2.5
A =15

11. Answer
Need Another Example?
The back of a dog house is composed of a square and
a triangle. How much wood is needed for the back of
the dog house to the nearest tenth of a square foot?
8.1 ft2

12. 1
Need Another Example?
2
3
4
Step-by-Step Example
3. Find the area of the
shaded region.
Area of rectangle
The area of the shaded region is 60 – 2 or
58 square inches.
Area of triangles
Find the area of the rectangle and
subtract the area of the four triangles.
ℓ = 12, w = 5
b = 1, h = 1
Simplify.
Simplify.
A = ℓw
A = 12 • 5
A = 60
A = 4 • bh
A = 4 • • 1 • 1
A = 2

13. Answer
Need Another Example?
Two congruent triangles are cut from a rectangle.
Find the area of the shaded region. Round to the
nearest tenth if necessary.
144 in2

14. 1
Need Another Example?
2
3
Step-by-Step Example
4. The blueprint for a hotel
swimming area is
represented by the figure
shown. The shaded area
represents the pool. Find
the area of the pool.
Area of the entire rectangle
Find the area of the entire rectangle and subtract the
section that is not shaded.
Area not shaded
The area of the shaded region is 1,050 – 440 or
610 square meters.
A = ℓw
A = 42 • 25 or 1,050
A = ℓw
A = 22 • 20 or 440

15. Answer
Need Another Example?
Mario sketched a drawing of a dirt bike track he wants his dad to
build. The brown area represents the track. Find the area of the
track. Round to the nearest tenth.
2,590.5 ft2

16. How did what you learned
today help you answer the
Course 2, Lesson 8-3
Geometry
HOW do measurements help you
describe real-world objects?

17. How did what you learned
today help you answer the
Course 2, Lesson 8-3
Geometry
HOW do measurements help you
describe real-world objects?
Sample answers:
• To find the area of a composite figure, such as a
miniature golf course hole
• To find the area of the shaded portion of a figure, such
as the blueprint of a swimming pool area

18. What measurements would
you need to know in order to
find the area of the figure at
the right? What steps would
you take to find its area?
Course 2, Lesson 8-3
Ratios and Proportional RelationshipsFunctionsGeometry