Question

A car travel from a to b with a speed of 40km/h and returns back with a speed of 50km/h.Find its average speed over the journey.

Answer 1

Let the distance be x.
To cover 40 km, it takes 1 hr.
To cover x km, it will take x/40 hr.
To cover 60 km, it takes 1 hr.
To cover x km, it will take x/60 hr.
Total time taken=x/40+x/60
=5x/240
Average speed=x/(5x/240)
=x*240/5x
=48 km/hr