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A moving train passes a platform 50 metre long in 14 seconds and a lamp post in 10 seconds. The speed of the train (in km/h) is :
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- 24
- 36
- 40
- 45
Correct Option: D
Let the length of train be x metre.
When a train crosses a platform, distance covered by it = length of train and platform.
| ∴ Speed of train = | = | ||
| 14 | 10 |
| ⇒ | = | ||
| 7 | 5 |
⇒ 7x = 5x + 250
⇒ 7x – 5x = 250
| ⇒ 2x = 250 ⇒ x = | = 125 metre | |
| 2 |
| ∴ Speed of train = | |
| 10 |
| = |  |  | m./sec. | |
| 10 |
| = | | × | | kmph | ||
| 10 | 5 |
= 45 kmph
