Circumference and Parts of a Circle

​The Parts of a Circle: Circumference

​LET'S REVIEW

Multiple Choice

Does the graph represent a proportional relationship?

• Yes, it is proportional.

• No, it is NOT proportional.

Multiple Choice

Is this table proportional?

• yes
• no
• I'm not sure, I need extra help!

Multiple Choice

What is the formula for a proportional relationship?

• y=kx
• z=ykx
• y=ky

Multiple Choice

Determine the constant of proportionality for the table. Express your answer as y = kx

• x = 1/2y

• y = 2x

• k = x

​NEW INFORMATION

Circles have many different parts which we use in math.

​

​

We are going to go through them before moving on to how to find circumference.​

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​The Parts of a Circle

​

RADIUS

DEFINITION: The distance halfway across a circle- from center to circumference (half the diameter).

FORMULA: Diameter/2

DIAMETER

DEFINITION: The full distance across a circle -from one side to the opposite side passing through the center

FORMULA: Radius x 2

Multiple Choice

What is a straight line that goes through the center of a circle from side to opposite side?

• Diameter

• Circumference

• Radius

• Center

Multiple Choice

Does this picture show the diameter or radius of a circle?

• Diameter

• Radius

Multiple Choice

What is the line that goes from the center of a circle to any point on the circle?

• Diameter

• Circumference

• Chord

• Radius

Multiple Choice

Is the red line a radius or diameter of the circle?

• Radius
• Diameter

​NEW INFORMATION

Circumference

Pi

The ratio of a circle's circumference to its diameter.

​

Used to calculate the circumference and area of a circle.

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USE 3.14 to represent PI​

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Solve a Circumference Problem

1. Write the formula

2. Substitute the values

3. Multiply

4. Write the unit of measure

​TIME TO PRACTICE

Multiple Choice

Calculate the circumference of the circle. C =  $$\pi$$  d

• 98.91 ft.

• 63 ft.

• 197.82 ft.

Multiple Choice

What is Circumference?

• The distance around a circle.

• A line that connects the center to a point on the circle.

• A line that passes through the center of the circle.

Multiple Choice

Find the circumference of the circle

• 50.24 yd

• 25.12 yd

• 11.14 yd

Multiple Choice

Find the circumference of the circle

• 18.84 cm

• 75.36 cm

• 37.68 cm

Independent Work:

• Parts of a circle

• ​Circumference of a Circle

• Find the circumference of a circle when given diameter

​Some text here about the topic of discussion.

Independent Work