11.4

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Five-Minute Check (over Lesson 11–3)
Main Idea and Vocabulary
Key Concept: Area of a Circle
Example 1: Find the Area of a Circle
Example 2: Real-World Example
Example 3: Test Example
• Find the areas of circles.
• sector
Find the Area of a Circle
Find the area of the circle shown here.
A = πr2
Area of a circle
A = π ● 42
Replace r with 4.
π
× 4
x2
ENTER 50.26548246
Answer: about 50.3 cm2
Find the area of the circle shown here.
A. approximately
32.97 ft2
B. approximately
65.9 ft2
C. approximately
121.3 ft2
0%
D
0%
C
0%
B
A
D. approximately
346.4 ft2
0%
1.
2.
3.
4.
A
B
C
D
KOI Find the area of the koi
pond shown.
The diameter of the koi pond is 3.6 m. Therefore, the
radius is 1.8 m.
A = πr2
Area of a circle
A = π(1.8)2
Replace r with 1.8.
A ≈ 10.2
Multiply.
Answer: about 10.2 m2
COINS Find the area of a nickel whose diameter is
2.1 centimeters.
A. approximately 2.5 cm2
B. approximately 3.3 cm2
C. approximately 3.5 cm2
D. approximately 4.5 cm2
0%
0%
A
B
1.
2.
3.
4.
0%
C
A
B
C
D
0%
D
Mr. McGowan made an apple pie with a diameter of
10 inches. He cut the pie into 6 equal slices. Find
the approximate area of each slice.
A 3 in2
B 13 in2
C 16 in2
D 52 in2
Read the Item
You can use the diameter to find the total area of the pie
and then divide that result by 6 to find the area of each
slice.
Solve the Item
Find the area of the whole pie.
A = πr2
Area of a circle
A = π(5)2
Replace r with 5.
A ≈ 78
Multiply.
Find the area of one slice:
78 ÷ 6 = 13
Answer: B
MERRY-GO-ROUND The floor of a merry-go-round at
the amusement park has a diameter of 40 feet. The
floor is divided evenly into eight sections, each
having a different color. Find the approximate area of
each section of the floor.
A. 157 ft2
B. 225 ft2
1.
2.
3.
4.
C. 264 ft2
0%
D
0%
C
0%
B
0%
A
D. 312 ft2
A
B
C
D
End of the Lesson
Five-Minute Check (over Lesson 11–3)
Image Bank
Math Tools
Area of Trapezoids
Drawing 3-D Figures
Area of Polygons
(over Lesson 11-3)
Find the circumference of the circle. Use 3.14 for .
Round to the nearest tenth if necessary.
radius = 5 ft
A. 15.7 ft
B. 31.4 ft
C. 78.5 ft
D. 3.14 ft
0%
0%
A
B
1.
2.
3.
4.
0%
C
A
B
C
D
0%
D
(over Lesson 11-3)
Find the circumference of the circle. Use 3.14 for .
Round to the nearest tenth if necessary.
diameter = 11.2 in.
A. 35.2 in.
B. 17.6 in.
C. 70.3 in.
D. 7.0 in.
0%
0%
A
B
1.
2.
3.
4.
0%
C
A
B
C
D
0%
D
(over Lesson 11-3)
Find the diameter of the circle. Use 3.14 for .
Round to the nearest tenth if necessary.
C = 30 ft, diameter = ___ ft
A. 9.5
B. 19.1
C. 9.6
D. 4.8
0%
0%
A
B
1.
2.
3.
4.
0%
C
A
B
C
D
0%
D
(over Lesson 11-3)
Find the diameter of the circle. Use 3.14 for .
Round to the nearest tenth if necessary.
C = 96 cm, diameter = ___ cm
A. 24
B. 15.3
C. 3.0
D. 30.6
0%
0%
A
B
1.
2.
3.
4.
0%
C
A
B
C
D
0%
D
(over Lesson 11-3)
A coffee can has a circumference of 216 mm.
Which equation could be used to find the
diameter of the can in inches?
A. 216 = d
B. C =  × 108
C. 108 =  × d
D. C =  × 14.7
0%
0%
A
B
1.
2.
3.
4.
0%
C
A
B
C
D
0%
D
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