Two railway stations A and B are 380 km apart. Train-1 leaves station A at…
2023
Two railway stations A and B are 380 km apart. Train-1 leaves station A at 7:00 AM moving with a speed of 80 km/hour towards B. After half an hour Train-2 leaves station B towards A moving with speed of 90 km/hour. At what time, the two trains will cross each other?
Answer: C. 9:30 AM — ConceptWhen two objects move toward each other, their separation decreases at the sum of their speeds. If one starts earlier, first subtract the distance…
- A.
8:45 AM
- B.
9:00 AM
- C.
9:30 AM
- D.
10:15 AM
Show answer & explanation
Correct answer: C
Concept
When two objects move toward each other, their separation decreases at the sum of their speeds.
If one starts earlier, first subtract the distance covered during its head start; then divide the remaining separation by the relative speed.
Application
Train-1 travels for 0.5 hour before Train-2 starts, covering 80 × 0.5 = 40 km.
At 7:30 AM, the remaining separation is 380 − 40 = 340 km.
Once both trains move toward each other, their relative speed is 80 + 90 = 170 km/h.
The time from 7:30 AM to the meeting is 340 ÷ 170 = 2 hours.
Cross-check
By 9:30 AM, Train-1 covers 80 × 2.5 = 200 km and Train-2 covers 90 × 2 = 180 km. Their total distance is 200 + 180 = 380 km, exactly the distance between A and B.
Result
The trains cross at 9:30 AM.