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

Circumference

DEFINITION: length around the circle

FORMULA: 2 x pi x radius
- OR -
Diameter x pi

Pi

DEFINITION: The circumference divided by the diameter on any circle-same #, never terminates or repeats

FORMULA: Approximately 3.14

Multiple Choice

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

• Radius
• Diameter

Multiple Choice

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

• Radius
• Diameter

Multiple Choice

What does "circumference" mean?

• Space a circle takes up
• Distance around a circle
• Line from one side of a circle to another
• Line from center of circle to side

Multiple Choice

What is the radius?

• 18
• 72
• 38
• 14

Multiple Choice

What is the diameter?

• 8
• 16
• 10
• 4

Multiple Choice

What part of a circle does the red line represent?

• the radius

• the diameter

• the circumference

Multiple Choice

What part of a circle does the red line represent?

• the radius

• the diameter

• the circumference

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

What number is pi?

• 1.41

• 2.00

• 3.14

• 5.14

Multiple Choice

Which of these ways can you use to find pi?

• Circumference divided by the diameter

• Circumference divided by the radius

• radius times pi

• Circumference times diamter

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

The radius is twice the diameter.

• Yes it is!!!

• No it's not!!

Multiple Choice

If the radius is 4, the diameter is

• 2

• 4

• 8

• $$\pi$$

Multiple Choice

Which of these ways can you use to find pi?

• $$C\ \div d$$

• $$c\ \div\ r$$

• d x r

• $$c\ \times\ d$$

Multiple Choice

Which of these ways can you use to find pi?

• Circumference divided by the diameter

• Circumference divided by the radius

• radius times pi

• Circumference times diamter

Multiple Choice

The distance across a circle through the center is called the_______________.

• radius
• circumference
• diameter
• area

Multiple Choice

What is the radius if the diameter is 10 m ?

• 5
• 20
• 2

Multiple Choice

Which of these ways can you use to find pi?

• $$\frac{c}{d}$$

• $$\frac{c}{r}$$

• $$c\ \times\ \pi$$

• $$\frac{c}{\pi}$$

Multiple Choice

If the diameter of a circle is 24 ft, the radius is 48 ft.

• TRUE
• FALSE

Multiple Choice

If the diameter of a circle is 10 cm, the radius is 5 cm.

• TRUE
• FALSE

Multiple Choice

Which of these ways can you use to find pi?

• $$C\ \div d$$

• $$c\ \div\ r$$

• d x r

• $$c\ \times\ d$$