Finding Circumference, Radius, and Diameter of Circles

True or False: The radius goes half way across the circle

• False

• True

What is the formula for circumference of a circle given the diameter?

• C = π r

• C = 2 π r

• C = π d

• C = 2 π d

A cruise ship has a large, circular window. It has a diameter of 6 meters. What is the window's approximate circumference?

• 3 m 

• 9.42 m

• 12 m

• 18.84 m

A circle has a radius of 23 feet. What is the diameter of the circle?

• 23 feet

• 46 feet

• 1/2 feet

• none of the above

Which of the following names a radius?

• segment AC

• segment DB

• segment AB

• segement BC

Which of the following names a diameter?

• segment AC

• segment DB

• segment AB

• segment BC

What is circumference?

• The distance around a circle.

• The space inside the circle.

• A line from side to side passing through the center.

• A line from the center to the side.

What is the diameter?

• 8

• 16

• 10

• 4

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

• Radius

• Diameter

If you are given the diameter, how can you calculate the radius?

• Multiply the diameter by 2

• Divide the diameter by 2

• Add 2 to the diameter

• Subtract 2 from the diameter