Question: 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?
[A].10
12
15
20
[A].
[B].
[C].
[D].
Answer: Option B
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 |