A train moves from A to B and returns from B to A but the speed from A to B…
2024
A train moves from A to B and returns from B to A but the speed from A to B was 50 km/hr and the speed from B to A is 60 km/hr. What is the average speed of the train?
- A.
54.55 km/h
- B.
58.55 km/h
- C.
55.55 km/h
- D.
64.55 km/h
Attempted by 624 students.
Show answer & explanation
Correct answer: A
Key formula: For equal distances, the average speed = 2ab/(a+b).
Let the speed from A to B be a = 50 km/h and from B to A be b = 60 km/h.
Compute the harmonic mean: average = 2ab/(a+b) = 2*50*60/(50+60) = 6000/110 = 600/11.
Convert to decimal: 600/11 ≈ 54.545... km/h.
Answer: 54.55 km/h (approx).