Question

A scooterist goes to a place of 20km/hr and return at a speed of 30mm/hr. Find the average speed in km/hr for the entire ?

Answer 1

We can do this in different ways. I like this one:

Explanation:

Since we don't know the distance we will call this `D`.

The time for the out trip is `D/20` and the return trip will take `D/30` (in hours)

The total time will be `t=D/20+D/30=(3D)/60+(2D)/60=(5D)/60=D/12`
for a distance of `2D`

Average speed will be `2DdivD/12=2cancelDxx12/(cancelD)=24 \ "km/h"`.

Note:
Since this works for all distances (they cancel out in the end), you just could also have picked any convenient distance, like `60 \ "km"`:
Out `3` hours, home `2` hours, `120 \ "km"` in `5` hours, same result.