Bunuel
100-meter long train A and 150-meter long train B are moving towards each other, at 54 km/h and 36 km/h respectively. If a person in standing still in train A, how long will it take him to pass train B if the distance between him and the train B is 150 meters?
A. 15 seconds
B. 12 seconds
C. 10 seconds
D. 6 seconds
E. 5 seconds
Since train B is 150 meters long and the person in train A is 150 meters from train B, train A has to travel 150 + 150 = 300 meters for the person to pass train B. However, since both trains are moving toward each other, we can create the equation where t = the number of hours it takes for the person in train A to pass train B (notice that 300 meters = 0.3 km):
54t + 36t = 0.3
90t = 0.3
t = 0.3/90 = 3/900 = 1/300
Therefore, it takes 1/300 hour or 1/300 x 3600 = 12 seconds for the person in train A to pass train B.
Answer: B