Question

A car travell 30 km at uniform speed of 40km\hr and net 30km at a uniform speed of 20 km/hr find it average speed

Answer 1

average speed =total distance/total time
in first case
30=40×t1 ( d=s×t)
t1=3/4
in second case
30=20×t2
t2=3/2
average speed = 30+30/t1+t2
60/(3/4+3/2)
80/3