Two trains are moving in opposite directions at 90 km/hr and 72 km/hr respectively. Their lengths are 280 m and 530 m respectively. The time taken by them to cross each other in seconds is :

18 sec

12 sec

15 sec

21 sec

Relative speed = (90 +72) km/hr = 162 km/hr. = 162 * 5/18 = 45 m/sec Distance covered = (280 + 530) m = 810 m Required time = 810/45 = 18 sec.

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