Circumference Radius Diameter of a Circle

What is the formula to find the radius of a circle from its circumference?

• radius = circumference / π

• radius = circumference * π

• radius = circumference / (2 * π)

• radius = circumference * (2 * π)

What is the area of this circle?
d = 8cm

• 16π

• 8π

• 4π

• 36π

A tire has a radius of 14 inches. What is its diameter?

• 14 inches

• 7 inches

• 28 inches

A pond has a diameter of 12 feet. What is its radius?

• 12 feet

• 6 feet

• 24 feet

A cruise ship has a large, circular window with a diameter of 6 meters. Approximately what is the window's circumference?

• 18 meters

• 12 meters

• 19 meters

• 6 meters

The radius of the circle is 9 meters. What is the circle's circumference?

• 56.52 m

• 28.26 m

• 18 m

Serena drew a circle with a circumference of 157 centimeters. What is the approximate diameter of the circle she drew?

• 1.57 cm

• 50 cm

• 15.7 cm

• 25 cm

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

• Radius

• Diameter

Jayne has a very large circular lollipop that has a circumference of 25.12 inches. What would the diameter of Jayne’s lollipop be? Use π = 3.14.

• 4 in.

• 8 in.

• 12 in.

• 16 in.

Select all of the formulas below that can be used to find the circumference of a circle.

• πd

• πr²

• πdr

• 2rπd

• 2πr