I have a sample problem: Bob travels up a hill at $X$ miles an hour and down the hill at $Y$ miles an hour (You can assume that the length of the trail going up is the length of the trail going down in terms of distance).
If a question were to ask:
What is Bob's average speed in miles per hour?
How would I know whether the question is talking about the average miles per hour from a time perspective (where the answer would be the harmonic mean of $X$ and $Y$)?
Or if the question is asking about the average miles per hour from a distance perspective (where the arithmetic mean would be the answer)
To further clarify time perspective:
If $X = 3$, $Y = 12$ and the length of the hill is 3 miles:
The time it would take to go up the hill is one hour while the time it takes to go down the hill is 15 minutes. From a time perspective $X$ is four times more weighted than $Y$, not equally as weighted (they are equally weighted in the distance perspective since the distances up and down the hill are the same).
How would I go about a problem like the one "What is Bob's average speed in miles per hour?" My reason for this interest is due to my observation of a question that had the answer developed from a time perspective. I have also seen questions with the answers derived from a distance perspective.