How much time does a train 100 metres long running at 72 km/hr take to pass a pole?  Choose the correct choice from the following answers:
A) 7.9 s B) 2.5 s C) 5 s D) 7.6 s E) 7.4 s

Rationale: explanation : 72 km / hr = 72 * 5 / 18 = 20 m / s speed = distance / time ; v = d / t 20 = 100 / t t = 5 s answer : c
Answer: C