Two trains, each 100 m long, moving in opposite directions, cross each other in 8 seconds. If one is moving twice as fast the other, then the speed of the faster train is:

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Question:
Two trains, each 100 m long, moving in opposite directions, cross each other in 8 seconds. If one is moving twice as fast the other, then the speed of the faster train is:

[A].

30 km/hr

[B].

45 km/hr

[C].

60 km/hr

[D].

75 km/hr

Answer: Option C

Explanation:

Let the speed of the slower train be x m/sec.

Then, speed of the faster train = 2x m/sec.

Relative speed = (x + 2x) m/sec = 3x m/sec.

(100 + 100) = 3x
8

24x = 200

x = 25 .
3
So, speed of the faster train = 50 m/sec
3
   = 50 x 18 km/hr
3 5

   = 60 km/hr.