A train travels from Delhi to Mumbai at an average speed of 60 km/h and returns at an average speed of 40 km/h. Find the average speed of the train for the entire trip.
Correct: B
Let the distance between Delhi and Mumbai be x km. The time taken to travel from Delhi to Mumbai is x/60 hours, and the time taken to return is x/40 hours. The total distance traveled is 2x km, and the total time taken is x/60 + x/40 hours. The average speed is given by total distance/total time, which is 2x/(x/60 + x/40) = 2x/(2x/120 + 3x/120) = 2x/(5x/120) = 48 km/h.