Area and Circumference of a Circle

A circle has a diameter of 8 ft. Which measurement would be the circumference of the same circle? (use π ≈ 3.14)

The mean radius of Earth is 6,371.0 kilometers and the mean radius of Earth’s Moon is 1,737.5 kilometers. What is the approximate difference in the mean circumferences, in kilometers, of Earth and Earth’s Moon? Round your answer to the nearest tenth of a kilometer. Use 3.14 for π.

Jill slices an orange and a grapefruit and then measures the radius of each. She finds that the radius of the orange is 2.4 centimeters and the radius of the grapefruit is 4.8 centimeters. What is the approximate difference in the circumferences of the orange and the grapefruit? Round your answer to the nearest tenth of a centimeter. Use 3.14 for π.