A car travels from A to B at a speed of 40 km/hr, travels back from B to A at a speed of 30 km/hr and again goes from A to B at a speed of 60 km/hr. What is the average speed of the car?
Answer
The correct answer is A: 40 km/hr. Average speed = 3d/(d/40+d/30+d/60) = 3/((3+4+2)/120) = 3·120/9 = 40 km/hr.