Diameter and Radius of a Circle

If the diameter is 10, what is the circumference?

• 15.70796327

• 31.41592654

What is the formula for calculating the circumference of a circle?

• C = 2πr

• C = πr^2

• C = πd

• C = 2r

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)

The diameter of circle L is 20 units and the diameter of circle M is 13 units and QR = 4. Find LQ.

• 16 units

• 6 units

• 14 units

• 9 units

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

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

• πd

• πr²

• πdr

• 2rπd

• 2πr

I wrapped a tape measure around the trunk of the tree and it was 14.13 feet. What is the diameter of the tree? Use 3.14 for pi. Round to the nearest hundredth.

• 2.25 ft

• 44.37 ft

• 4.5 ft

• 17.27 ft

What is the area of this circle?

• 28.26 cm²

• 28.26 cm

• 9.42 cm²

• 9.42 cm