Two trains 230 m and 270 m long are running in opposite directions at speeds of 42 km/h and 48 km/h, respectively. They cross each other in:
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 20 seconds.
Converting speeds to m/s:
⇒ 42 km/h = 42 × (5/18) m/s = 11.67 m/s
⇒ 48 km/h = 48 × (5/18) m/s = 13.33 m/s
Calculating relative speed:
⇒ Relative speed = Speed of Train 1 + Speed of Train 2
⇒ Relative speed = 11.67 m/s + 13.33 m/s = 25 m/s
Calculating crossing time:
⇒ Time = Total length of trains / Relative speed
⇒ Time = (230 m + 270 m) / 25 m/s
⇒ Time = 500 m / 25 m/s
⇒ Time = 20 seconds
Therefore, the two trains cross each other in 20 seconds.