Problems on Trains
- 1. The length of the bridge, which a train 130 metres long and travelling at 45 km/hr can cross in 30 seconds, is:
Options- A. 200 m
- B. 225 m
- C. 245 m
- D. 250 m Discuss
Correct Answer: 245 m
Explanation:
| Speed = | ❨ | 45 x | 5 | ❩m/sec | = | ❨ | 25 | ❩m/sec. |
| 18 | 2 |
Time = 30 sec.
Let the length of bridge be x metres.
| Then, | 130 + x | = | 25 |
| 30 | 2 |
⟹ 2(130 + x) = 750
⟹ x = 245 m.
- 2. 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.
- 3. A train passes a station platform in 36 seconds and a man standing on the platform in 20 seconds. If the speed of the train is 54 km/hr, what is the length of the platform?
Options- A. 120 m
- B. 240 m
- C. 300 m
- D. None of these Discuss
Correct Answer: 240 m
Explanation:
| Speed = | ❨ | 54 x | 5 | ❩m/sec = 15 m/sec. |
| 18 |
Length of the train = (15 x 20)m = 300 m.
Let the length of the platform be x metres.
| Then, | x + 300 | = 15 |
| 36 |
⟹ x + 300 = 540
⟹ x = 240 m.
- 4. Two trains of equal length are running on parallel lines in the same direction at 46 km/hr and 36 km/hr. The faster train passes the slower train in 36 seconds. The length of each train is:
Options- A. 50 m
- B. 72 m
- C. 80 m
- D. 82 m Discuss
Correct Answer: 50 m
Explanation:
Let the length of each train be x metres.
Then, distance covered = 2x metres.
Relative speed = (46 - 36) km/hr
| = | ❨ | 10 x | 5 | ❩m/sec |
| 18 |
| = | ❨ | 25 | ❩m/sec |
| 9 |
| ∴ | 2x | = | 25 |
| 36 | 9 |
⟹ 2x = 100
⟹ x = 50.
- 5. 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.
- 6. A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is:
Options- A. 45 km/hr
- B. 50 km/hr
- C. 54 km/hr
- D. 55 km/hr Discuss
Correct Answer: 50 km/hr
Explanation:
| Speed of the train relative to man = | ❨ | 125 | ❩m/sec |
| 10 |
| = | ❨ | 25 | ❩m/sec. |
| 2 |
| = | ❨ | 25 | x | 18 | ❩km/hr |
| 2 | 5 |
= 45 km/hr.
Let the speed of the train be x km/hr. Then, relative speed = (x - 5) km/hr.
∴ x - 5 = 45 ⟹ x = 50 km/hr.
- 7. A train running at the speed of 60 km/hr crosses a pole in 9 seconds. What is the length of the train?
Options- A. 120 metres
- B. 180 metres
- C. 324 metres
- D. 150 metres Discuss
Correct Answer: 150 metres
Explanation:
| Speed = | ❨ | 60 x | 5 | ❩m/sec | = | ❨ | 50 | ❩m/sec. |
| 18 | 3 |
Length of the train = (Speed x Time).
| ∴ Length of the train = | ❨ | 50 | x 9 | ❩m = 150 m. |
| 3 |
- 8. A train 360 m long is running at a speed of 45 km/hr. In what time will it pass a bridge 140 m long?
Options- A. 40 sec
- B. 42 sec
- C. 45 sec
- D. 48 sec Discuss
Correct Answer: 40 sec
Explanation:
| Formula for converting from km/hr to m/s: X km/hr = | ❨ | X x | 5 | ❩ | m/s. |
| 18 |
| Therefore, Speed = | ❨ | 45 x | 5 | ❩m/sec | = | 25 | m/sec. |
| 18 | 2 |
Total distance to be covered = (360 + 140) m = 500 m.
| Formula for finding Time = | ❨ | Distance | ❩ |
| Speed |
| ∴ Required time = | ❨ | 500 x 2 | ❩sec | = 40 sec. |
| 25 |
- 9. A train 800 metres long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 minute, then the length of the tunnel (in meters) is:
Options- A. 130
- B. 360
- C. 500
- D. 540 Discuss
Correct Answer: 500
Explanation:
| Speed = | ❨ | 78 x | 5 | ❩ | m/sec | = | ❨ | 65 | ❩ | m/sec. |
| 18 | 3 |
Time = 1 minute = 60 seconds.
Let the length of the tunnel be x metres.
| Then, | ❨ | 800 + x | ❩ | = | 65 |
| 60 | 3 |
⟹ 3(800 + x) = 3900
⟹ x = 500.
- 10. Two, trains, one from Howrah to Patna and the other from Patna to Howrah, start simultaneously. After they meet, the trains reach their destinations after 9 hours and 16 hours respectively. The ratio of their speeds is:
Options- A. 2 : 3
- B. 4 : 3
- C. 6 : 7
- D. 9 : 16 Discuss
Correct Answer: 4 : 3
Explanation:
Let us name the trains as A and B. Then,
(A's speed) : (B's speed) = √b : √a = √16 : √9 = 4 : 3.
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