Question

A car moving on a straight road covers one third of distance with speed of 20 km/h and the rest with a speed of 60 km/h. The average speed of car is......?

Answer 1

Average velocity = Total displacement / Total time
= S / (t1 + t2)
= S / (S/(3v1) + 2S/(3v2))
= 1 / (1/(3v1) + 2/(3v2))
= 3v1v2 / (v2 + 2v1)
= 3*20*60 / (60 + 2*20)
= 36 km/h