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2. Firefox user, right? It should be fixed now. Thank you for reporting this issue. 1. You reminded me of another nice example of wrong shortcuts. Average spee
by mlajtos 3y ago
2. Firefox user, right? It should be fixed now. Thank you for reporting this issue.
1. You reminded me of another nice example of wrong shortcuts. Average speed of car from city A to city B is 120km/h. Average speed back (B -> A) was 80km/h. What was the average speed of the car on the whole path (A -> B -> A)? It's not 100km/h.
- firstlink 3y ago> It's not 100km/h. Of course it is... if you're averaging over distance. There's no reason that's less valid than whichever average you have in mind.
- joebiden2 3y agoHow do you arrive at 100km/h if you're averaging over distance? I don't doubt you're right, but I don't see it. My calculation is as follows: suppose the distance between both cities is 120km. The trip A -> B thus takes exactly one hour. The trip B -> A takes 1.5 hours (120km / 80km/h) = 1.5h. The total trip therefore takes 2.5h, the total distance is 240km, which averages at 96km/h (240/(1 + 1.5)). A simple (V1 + V2)/2 is surely possible, but I don't see the value of that average, I can't think of a situation where it would be useful.
- mlajtos 3y agoYou are right. Harmonic mean is the right tool.
- tkot 3y agoI think you are thinking about a case where someone goes 120km/h for 1 hour and then 80km/h for 1 hour instead of going over a fixed distance at 120km/h and then going over the same distance at 80km/h.
- youainti 3y agoTo be pedantic, 100km/h is the arithmetic mean. Of course this is the wrong tool to use (which is your point) but 100km/h is the correct answer if by mean you intend to say arithmetic mean.