A 600 meters long train crosses its two times long bridge in 90 seconds and the same train crosses another train which is moving in opposite direction in 36 seconds. If the speed of second train is 6 km/hr more than first train, then find the length of second train.

Correct option is E

Length of bridge = 1200 meter
Speed of train =(600+1200)/90=20m/s =20×18/5=72 kmph
Speed of train X =72+6=78 kmph
Let required length be L meter.
ATQ,
(600+L)=36×(72+78)×5/18
600+L=1500
L=900 meters