Question

calculate the average speed for
a round trip with a “going” average speed of 30 miles per hour and a
“returning” average speed of 60 miles per hour

Answer 1

40

Answer 2

could you please explain :) @zarkon

Answer 3

... for potential readers

Answer 4

@Australopithecus : your answer is wrong

Answer 5

Let 2d be the round trip distance.
Average speed would be 2d divided by the time to travel a distance of 2d.\[t=\frac{d}{r} \]The time out is\[t=\frac{d}{30} \]and\[t=\frac{d}{60} \] is the time to return.\[\frac{2d}{\frac{d}{30}+\frac{d}{60}}=40 \text{ mph} \]

Answer 6

@robtobey :)

Answer 7

this is one of the tricky problems ....