Subject: General Aptitude · Chapter: Problems on Trains · Exam: 2009 · Marks: · Difficulty:
Two trains 200 metres and 150 metres long are running on parallel rails in the same direction at speeds of 40 km/hr and 45 km/hr respectively. Time taken by the faster train to cross the slowed train will be
(a)72 seconds
(b)132 seconds
(c)192 seconds
(d)252 seconds
Answer
Answer (as printed): D
Explanation
Relative speed $=(45-40) \mathrm{km} / \mathrm{hr}=5 \mathrm{km} / \mathrm{hr}$ $$=\left(5 \times \frac{5}{18}\right) \mathrm{m} / \mathrm{sec}=\left(\frac{25}{18}\right) \mathrm{m} / \mathrm{sec} .$$ Total distance covered = Sum of lengths of trains = (200 + 150) m = 350 m . $$\text { ∴ Time taken }=\left(350 \times \frac{18}{25}\right) \mathrm{sec}=252 \mathrm{sec} .$$