Transcript Glencoe Mathematics

Five-Minute Check (over Lesson 10–1)
Main Idea and Vocabulary
Key Concepts: Radius and Diameter
Example 1: Find the Radius
Example 2: Find the Diameter
Key Concept: Circumference
Example 3: Estimate the Circumference
Example 4: Estimate the Circumference
Example 5: Use a Calculator to Find Circumference
Example 6: Choose the Correct Method
• Estimate and find the circumference of circles.
• circle
• center
• chord
• diameter
• circumference
• radius
Find the Radius
The diameter of a circle is 48 centimeters. Find the
radius.
d
Answer: The radius is 24 centimeters.
The diameter of a circle is 16 meters. Find the
radius.
A. 2 m
B. 8 m
C. 16 m
D. 32 m
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Find the Diameter
The radius of a circle is 9 inches. Find the diameter.
d = 2r
Diameter of circle
Answer: The diameter is 18 inches.
The radius of a circle is 22 centimeters. Find the
diameter.
A. 11 cm
B. 22 cm
C. 44 cm
D. 88 cm
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Estimate the Circumference
Estimate the circumference of the circle.
C = πd
Replace π with 3 and d with 6.
Answer: The circumference is about 18 meters.
Estimate the circumference of the circle.
A. 6 yd
B. 8 yd
C. 12 yd
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Estimate the Circumference
Estimate the circumference of the circle.
C = 2πr
Replace π with 3 and r with 15.
Answer: The circumference is about 90 millimeters.
Estimate the circumference of the circle.
A. 8 in.
B. 12 in.
C. 24 in.
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D. 72 in.
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Use a Calculator to Find Circumference
Use a calculator to find the circumference
of the circle. Round to the nearest tenth.
C = 2πr
C=2●π●3
Replace r with 3.
2 × π
18.84955592
× 3 ENTER
Answer: Rounded to the nearest tenth, the
circumference is 18.8 yards.
Use a calculator to find the circumference
of the circle. Round to the nearest tenth.
A. 7.9 cm
B. 15.7 cm
C. 37.7 cm
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D. 75.4 cm
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Choose the Correct Method
Anna knows the diameter of a basketball hoop but
would like to find the circumference. Which method
can she use to find the circumference of the
basketball hoop?
A Divide the diameter by π.
B Multiply the radius by π.
C Multiply the diameter by 2, and then multiply by π.
D Multiply the diameter by π.
Read the Item
You need to find the circumference of the basketball hoop.
You know the diameter of the basketball hoop.
Choose the Correct Method
Solve the Item
Use the formula for the circumference of a circle, C = πd.
The formula states that the circumference of a circle is
equal to π times the diameter.
Answer: D
A standard baseball has a circumference of 9 inches.
Which method can be used to find the radius of the
baseball?
A. Divide the circumference by π
and then multiply by 2.
B. Divide the circumference by π
and then divide by 2.
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D. Multiply the circumference by π
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C. Multiply the circumference by π
and then multiply by 2.
End of the Lesson
Five-Minute Check (over Lesson 10–1)
Image Bank
Math Tools
Using a Net to Build a Cube
Area of Triangles
(over Lesson 10-1)
Find the perimeter of the figure.
A. 10 in.
B. 11 in.
C. 12 in.
D. 22 in.
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(over Lesson 10-1)
Find the perimeter of the figure.
A.
48 ft
B.
83 ft
C.
96 ft
D.
166 ft
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(over Lesson 10-1)
Find the perimeter of the figure.
15 cm
A. 145 cm
9 cm
B. 48 cm
C. 24 cm
D. 12 cm
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(over Lesson 10-1)
Find the perimeter of the figure.
A. 34 m
B. 51 m
C. 68 m
D. 85 m
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(over Lesson 10-1)
What is the perimeter of a rectangular parking lot
that measures 52 feet by 128 feet?
A. 75 ft
B. 150 ft
C. 232 ft
D. 360 ft
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(over Lesson 10-1)
What is the length of a piece of paper that is
10 inches wide and has a perimeter of 44 inches?
A. 12 in.
B. 11 in.
C. 10 in.
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