Two trains 240 m and 180 m long run at the speed of 200 km/hr and 160 km/hr respectively in opposite direction on parallel tracks. Then time (in second) taken to cross each other is

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Question

This question was previously asked in

Kerala PSC Common Preliminary Exam (GRADUATE LEVEL) PYP - 127/22

Answer 1

Given:

Length of train 1 = 240 m

Speed of train 1 = 200 km/hr

Length of train 2 = 180 m

Speed of train 2 = 160 km/hr

Formula used:

Time taken to cross each other = \(\dfrac{\text{Sum of lengths of trains}}{\text{Relative speed}}\)

Relative speed (opposite direction) = Speed₁ + Speed₂

Calculations:

Relative speed = 200 km/hr + 160 km/hr

⇒ Relative speed = 360 km/hr

⇒ Relative speed = 360 × \(\dfrac{5}{18}\) m/s

⇒ Relative speed = 100 m/s

Sum of lengths of trains = 240 m + 180 m

⇒ Sum of lengths = 420 m

Time taken = 420/100

⇒ Time taken = 4.2 seconds

∴ The correct answer is option (4).

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