Problems on Trains
- 1. A train speeds past a pole in 15 seconds and a platform 100 m long in 25 seconds. Its length is:
Options- A. 50 m
- B. 150 m
- C. 200 m
- D. Data inadequate Discuss
Correct Answer: 150 m
Explanation:
Let the length of the train be x metres and its speed by y m/sec.
| Then, | x | = 15 ⟹ y = | x | . |
| y | 15 |
| ∴ | x + 100 | = | x |
| 25 | 15 |
⟹ 15(x + 100) = 25x
⟹ 15x + 1500 = 25x
⟹ 1500 = 10x
⟹ x = 150 m.
- 2. A jogger running at 9 kmph alongside a railway track in 240 metres ahead of the engine of a 120 metres long train running at 45 kmph in the same direction. In how much time will the train pass the jogger?
Options- A. 3.6 sec
- B. 18 sec
- C. 36 sec
- D. 72 sec Discuss
Correct Answer: 36 sec
Explanation:
Speed of train relative to jogger = (45 - 9) km/hr = 36 km/hr.
| = | ❨ | 36 x | 5 | ❩m/sec |
| 18 |
= 10 m/sec.
Distance to be covered = (240 + 120) m = 360 m.
- 3. A train moves past a telegraph post and a bridge 264 m long in 8 seconds and 20 seconds respectively. What is the speed of the train?
Options- A. 69.5 km/hr
- B. 70 km/hr
- C. 79 km/hr
- D. 79.2 km/hr Discuss
Correct Answer: 79.2 km/hr
Explanation:
Let the length of the train be x metres and its speed by y m/sec.
| Then, | x | = 8 ⟹ x = 8y |
| y |
| Now, | x + 264 | = y |
| 20 |
⟹ 8y + 264 = 20y
⟹ y = 22.
| ∴ Speed = 22 m/sec = | ❨ | 22 x | 18 | ❩ | km/hr = 79.2 km/hr. |
| 5 |
- 4. A 270 metres long train running at the speed of 120 kmph crosses another train running in opposite direction at the speed of 80 kmph in 9 seconds. What is the length of the other train?
Options- A. 230 m
- B. 240 m
- C. 260 m
- D. 320 m
- E. None of these Discuss
Correct Answer: 230 m
Explanation:
Relative speed = (120 + 80) km/hr
| = | ❨ | 200 x | 5 | ❩m/sec |
| 18 |
| = | ❨ | 500 | ❩m/sec. |
| 9 |
Let the length of the other train be x metres.
| Then, | x + 270 | = | 500 |
| 9 | 9 |
⟹ x + 270 = 500
⟹ x = 230.
- 5. A train 110 metres long is running with a speed of 60 kmph. In what time will it pass a man who is running at 6 kmph in the direction opposite to that in which the train is going?
Options- A. 5 sec
- B. 6 sec
- C. 7 sec
- D. 10 sec Discuss
Correct Answer: 6 sec
Explanation:
Speed of train relative to man = (60 + 6) km/hr = 66 km/hr.
| = | ❨ | 66 x | 5 | ❩m/sec |
| 18 |
| = | ❨ | 55 | ❩m/sec. |
| 3 |
| ∴ Time taken to pass the man = | ❨ | 110 x | 3 | ❩sec = 6 sec. |
| 55 |
- 6. Two trains are moving in opposite directions @ 60 km/hr and 90 km/hr. Their lengths are 1.10 km and 0.9 km respectively. The time taken by the slower train to cross the faster train in seconds is:
Options- A. 36
- B. 45
- C. 48
- D. 49 Discuss
Correct Answer: 48
Explanation:
Relative speed = (60+ 90) km/hr
| = | ❨ | 150 x | 5 | ❩m/sec |
| 18 |
| = | ❨ | 125 | ❩m/sec. |
| 3 |
Distance covered = (1.10 + 0.9) km = 2 km = 2000 m.
| Required time = | ❨ | 2000 x | 3 | ❩sec = 48 sec. |
| 125 |
- 7. A goods train runs at the speed of 72 kmph and crosses a 250 m long platform in 26 seconds. What is the length of the goods train?
Options- A. 230 m
- B. 240 m
- C. 260 m
- D. 270 m Discuss
Correct Answer: 270 m
Explanation:
| Speed = | ❨ | 72 x | 5 | ❩m/sec | = 20 m/sec. |
| 18 |
Time = 26 sec.
Let the length of the train be x metres.
| Then, | x + 250 | = 20 |
| 26 |
⟹ x + 250 = 520
⟹ x = 270.
- 8. Two trains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post. If the length of each train be 120 metres, in what time (in seconds) will they cross each other travelling in opposite direction?
Options- A. 10
- B. 12
- C. 15
- D. 20 Discuss
Correct Answer: 12
Explanation:
| Speed of the first train = | ❨ | 120 | ❩ | m/sec = 12 m/sec. |
| 10 |
| Speed of the second train = | ❨ | 120 | ❩ | m/sec = 8 m/sec. |
| 15 |
Relative speed = (12 + 8) = 20 m/sec.
| ∴ Required time = | [ | (120 + 120) | ] | sec = 12 sec. |
| 20 |
- 9. Two stations A and B are 110 km apart on a straight line. One train starts from A at 7 a.m. and travels towards B at 20 kmph. Another train starts from B at 8 a.m. and travels towards A at a speed of 25 kmph. At what time will they meet?
Options- A. 9 a.m.
- B. 10 a.m.
- C. 10.30 a.m.
- D. 11 a.m. Discuss
Correct Answer: 10 a.m.
Explanation:
Suppose they meet x hours after 7 a.m.
Distance covered by A in x hours = 20x km.
Distance covered by B in (x - 1) hours = 25(x - 1) km.
∴ 20x + 25(x - 1) = 110
⟹ 45x = 135
⟹ x = 3.
So, they meet at 10 a.m.
- 10. A train travelling at 48 kmph completely crosses another train having half its length and travelling in opposite direction at 42 kmph, in 12 seconds. It also passes a railway platform in 45 seconds. The length of the platform is
Options- A. 400 m
- B. 450 m
- C. 560 m
- D. 600 m Discuss
Correct Answer: 400 m
Explanation:
Let the length of the first train be x metres.
| Then, the length of the second train is | ❨ | x | ❩ | metres. |
| 2 |
| Relative speed = (48 + 42) kmph = | ❨ | 90 x | 5 | ❩ | m/sec = 25 m/sec. |
| 18 |
| ∴ | [x + (x/2)] | = 12 or | 3x | = 300 or x = 200. |
| 25 | 2 |
∴ Length of first train = 200 m.
Let the length of platform be y metres.
| Speed of the first train = | ❨ | 48 x | 5 | ❩ | m/sec = | 40 | m/sec. |
| 18 | 3 |
| ∴ (200 + y) x | 3 | = 45 |
| 40 |
⟹ 600 + 3y = 1800
⟹ y = 400 m.
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