Radius, Diameter, Circumference

What two formulas can you use to find the circumference?

• C = π·d

• C = π·r²

• C = 2·π·r

• C = d²

Select all the expressions that represent Circumference.

• $d\cdot r$

• $d\cdot\pi$

• $r\cdot\pi$

• $2r\cdot\pi$

• $2d\cdot\pi$

What questions do you still have about finding circumference, diameter, and radius?

A circle has only one radius.

• True
• False

Find the circumference of the circle.

• 78.5 cm

• 15.7 cm

• 7.85 cm

• 19.6 cm

The following circle has a circumference of 12.56 cm. What is the diameter?

• 2 cm

• 4 cm

• 39.44 cm

• 0.25 cm

Find the circumference of the circle.

• 18.8 cm

• 113 cm

• 37.7 cm

• 452.2 cm

What is the distance around a circle?

• Circumference
• Area
• Diameter
• Radius

Find the circumference of Circle C.

•  $75\pi\ cm$ 

•  $10\pi\ cm$ 

•  $5\pi\ cm$ 

•  $25\pi\ cm$ 

A circle has a circumference of 28.26 inches. What is the radius of the cirlce?

• 4.5 in

• 9 in

• 88.74 in

• 0.111111... in