Question

A car travels a certain distance with a speed of 40ms and return with speed u .if the average speed of the whole journey is 48ms . What is the value of u

Answer 1

2D/D/40+D/u=48  

80u=48u+1920

u=60m/s

2D is distance of combined journey

D/40 is time taken to reach the destination

D/u is taken taken to return from destination

Answer 2

Do it on your own....