Over Lesson 11–8
Find the area of a circle to the
nearest tenth.
A. A
Rebecca cuts a round piece of cardboard to use to
make a top hat. The diameter is 7.5 centimeters.
B. B
What is the area of the cardboard circle?
C. C
D. D
You found the areas of parallelograms,
triangles, and trapezoids. (Lesson 11–6)
• Find the area of composite figures.
• Solve problems involving the area of
composite figures.
• composite figure
A figure that is made up of two or more
shapes
Find the Area of Composite Figures
Find the area of the composite figure. Round to the
nearest tenth if necessary.
First, separate the figure into a triangle, square, and a
quarter-circle. Then find the sum of the areas of the
figure.
Find the Area of Composite Figures
Area of a triangle
b = 2 and h = 4
Simplify.
Find the Area of Composite Figures
A = s2
Area of a square
A = 22
s=2
A = 4
Simplify.
Find the Area of Composite Figures
Area of a
quarter-circle
r=2
Simplify.
Find the Area of Composite Figures
Total Area
A = 4 + 4 + 3.1
Add
the areas
A = 11.1 in2
Simplify
Answer: The area is about 11.1 square inches.
Find the area of the figure to the nearest tenth.
A. 71.1 cm2
B. 58.6 cm2
C. 58.3 cm2
D. 52.3 cm2
A.
B.
C.
D.
A
B
C
D
Solve Multi-Step Problems
CARPETING Carpeting costs $2 per square foot.
How much will it cost to carpet the area shown?
Understand
You know the
dimensions of the
figure. You need to
find its area.
Plan
First, separate the
figure into a rectangle,
a square, and a
triangle. Then find the
sum of the areas of
the figure.
Solve Multi-Step Problems
Solve
Step 1 Find the area to be carpeted.
Area of Rectangle
A = bh
Area of a rectangle
A = (14)(10)
Replace b with 14
and h with 10.
A = 140
Simplify.
Solve Multi-Step Problems
Solve
Area of Square
A = s2
Area of a square
A = 32
Replace s with 3.
A=9
Simplify.
Solve Multi-Step Problems
Solve
Area of Triangle
Area of a triangle
Replace b with 14
and h with 12.
Simplify.
The area to be carpeted is140 + 9 + 84 or 233 square
feet.
Solve Multi-Step Problems
Step 2 Find the cost of the carpeting.
2(233) = 466
Answer: So, it will cost $466 to carpet
the area shown.
Check The area of the figure should
be a little less than the area of a
rectangle that is 14 feet by 22 feet.
Since the area of a 14-by-22-foot
rectangle is 308 square feet, the
answer of an area of 233 square feet is
reasonable.
PAINTING One gallon of paint
is advertised to cover 100
square feet of wall surface.
About how many gallons will
be needed to paint the wall
shown?
A. about 3 gallons
B. about 4 gallons
C. about 5 gallons
D. about 6 gallons
A.
B.
C.
D.
A
B
C
D