My cycling friends and I are having a disagreement or maybe just a lively discussion about rotating pace lines. The problem is as follows: If the fast side of a rotating pace line is going 20 mph and the slow side is going 18 mph what is the average speed of the group from point A to point B. My contention is that if the fast side is always going 20 mph then the group will average 20 mph. However, some do not agree since they say that if you are going 18 mph some of the time you cannot average 20 mph, it would be something less than 20 mph (like 19 mph if you were going 20 mph half the time and 18 mph half the time - which is probably not the case). I have not figured out how to prove this one way or the other mathematically yet - too many variables.

Has anyone ever figured this out????????