The mean radius of earth is 6371 kilometers and the the mean radius of earth's moon is 1737.5 kilometers. what is is the approximate difference in the mean circumferences , in kilometers , of the earth's and earth's moon ? round your answer to the nearest tenth of a kilometer

The circumference is calculated through the equation,
                                C = 2πr
where C is circumference and r is radius.

Earth: 
                            C = 2π(6371 km)
                                = 40030.17 km

Moon:
                            C = 2π(1737.5 km)
                               = 10917.03 km
The difference between the two circumferences is approximately 29113.13 km.

Two because two of one thing is two.