An express train traveling at 72 kn/hr speed crosses a goods train traveling…
2025
An express train traveling at 72 kn/hr speed crosses a goods train traveling at 45 km/hr speed in the opposite direction in half a minute . Alternatively , if the express train were to overtake the goods train , how long will it take to accomplish the task . Assume that the trains continue to travel at the same respective speeds as mentioned in case 1.
Answer: D. 130 sec — Given: an express train at 72 km/h and a goods train at 45 km/h. They cross in opposite directions in 30 seconds. Step 1 — Find the total length of the two…
- A.
120 sec
- B.
100 sec
- C.
150 sec
- D.
130 sec
Attempted by 2 students.
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Correct answer: D
Given: an express train at 72 km/h and a goods train at 45 km/h. They cross in opposite directions in 30 seconds.
Step 1 — Find the total length of the two trains:
Relative speed when moving in opposite directions = 72 + 45 = 117 km/h.
30 seconds = 30/3600 = 1/120 hour.
Total length (sum of both trains) = 117 × 1/120 = 39/40 km.
Step 2 — Time to overtake when moving in the same direction:
Relative speed when moving in the same direction = 72 − 45 = 27 km/h.
Time (hours) = (total length) / relative speed = (39/40) / 27 = 39/1080 hours.
Convert to seconds: 39/1080 × 3600 = 39 × (3600/1080) = 39 × 10/3 = 130 seconds.
Answer: 130 seconds.