If the lengths of the two trains A and B are 400 m and 500 m respectively, then what is the time taken by them to cross each other?
Consider the following for the next three (03) items that follow: Two trains A and B started from stations P and Q respectively towards each other. Train A started at 7 p.m. at a speed of 60 km/hr and train B started at 4 a.m. (next day) at a speed of 90 km/hr. The distance between the two stations P and Q is 800 km.
- A. 21.6 seconds ✓
- B. 18.2 seconds
- C. 17.4 seconds
- D. 15.4 seconds
Correct Answer: A. 21.6 seconds
Explanation
When two trains cross each other in opposite directions, the total distance to cover is the sum of their lengths: 400 + 500 = 900 m. Their relative speed is 60 + 90 = 150 km/hr. To convert this to m/s, multiply by \frac{5}{18}, resulting in \frac{750}{18} = \frac{125}{3} m/s. The time taken to completely cross is \text{Distance} / \text{Speed} = \frac{900}{(125/3)} = \frac{2700}{125} = 21.6 seconds.
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