Circumference 7th grade

Circumference -

7th grade

By Kathy Hobbs

Which is the diameter?

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Which is the radius?

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Which is the center?​

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Where is the circumference?​

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Discuss where they all are. Which one is the longest? The shortest?

Label the circle

​D

​B

​C

​A

Multiple Choice

What is the purple line in the picture called?

• circumference

• diameter

• radius

• center

Multiple Choice

What is the blue line in the picture called?

• circumference

• diameter

• radius

• center

Multiple Choice

What is the perimeter of a circle called?

• circumference

• diameter

• radius

• center

Diameter = 2 times radius

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Radius = diameter divided by 2

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Which is longer?​

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Radius and Diameter

Write down the three formulas to find circumference.

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Pi is about 3.14... AND 22/7

Circumference

Multiple Choice

You can find the circumference by...

• multiplying 3.14 times the diameter

• the distance in the middle of the circle

• half the diameter

• twice the radius

Multiple Choice

The radius is

• 3.14... or 22/7

• the distance in the middle of the circle

• half the diameter

• twice the radius

Multiple Choice

The diameter is

• 3.14... or 22/7

• the distance in the middle of the circle

• half the diameter

• twice the radius

Multiple Choice

Pi is...

• 3.14... or 22/7

• the distance in the middle of the circle

• half the diameter

• twice the radius

The diameter of a circle is 14 inches. What is the radius of the circle?

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Example 1

Multiple Choice

The diameter of a circle is 20 cm. What's the radius?

• 40 cm

• 30 cm

• 20 cm

• 10 cm

Multiple Choice

The diameter of a circle is 7 ft. What's the radius?

• 5 ft

• 14 ft

• 3.5 ft

• 2.5 ft

Multiple Choice

The diameter of a circle is 60 ft. What's the radius?

• 20 ft

• 30 ft

• 3 ft

• 40 ft

The radius of a circle is 8 feet. What's the diameter?

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Example 2

Multiple Choice

The radius of a circle is 9 ft. What is the diameter?

• 4.5 ft

• 18 ft

• 20 ft

• 16 ft

Multiple Choice

The radius of a circle is 19 ft. What is the diameter?

• 40 ft

• 36 ft

• 38 ft

• 9.5 ft

Use either 3.14 OR 22/7

If the radius is 21, what is the circumference?

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​Some text here about the topic of discussion.

Find Circumference

Multiple Choice

If the diameter is 10 ft, what is the circumference (about)?

(Remember C = pi times diameter)

• 22/7

• 3.14

• 0.314

• 31.4

Multiple Choice

If the radius is 5 ft, what is the circumference (about)?

(Remember C = pi times diameter)

• 22/7

• 3.14

• 0.314

• 31.4

Multiple Choice

Big Ben is a famous clock tower in London, England. The diameter of the clock face is 23 feet. Determine the circumference of the clock face. Round to the nearest tenth.

• 3.14(11.5) or

  about 36.11 ft

• 3.14(23) or

  about 72.2 ft