Question

A person starts with the speed of u/1 kmph and returns with the speed of u/2 kmph, what is his average speed.

Answer 1

let the distance be X
therefore total distance =2x

time = distance /speed
time 1 = x/u/1 = x*1/u
=x/u
time2 = x/u/2 = x*2/u
=2x/u
average speed = 2x/x/u+2x/u
=2x/3x/u
=2x*u/3x
= 2u/3
hope it will help