2013gmat wrote:

Trains A and B travel at the same constant rate in opposite directions along the same route between Town G and Town H. If, after traveling for 2 hours, Train A passes Train B, how long does it take Train B to travel the entire distance between Town G and Town H?

(1) Train B started traveling between Town G and Town H 1 hour after Train A started traveling between Town H and Town G.

(2) Train B travels at the rate of 150 miles per hour.

Lets say the speed of the two trains is = a miles per hour,

the distance between the two towns as D miles.

Since the two trains travel in opposite direction, their relative speed = a + a = 2a miles per hour

Total time of travel till they pass each other = 2 hours & we are asked to find time taken for train B to travel the whole distance = D/a

Statement 1:

Train B started traveling between Town G and Town H 1 hour after Train A started traveling between Town H and Town G

Hence we have train A traveled alone for 1 hour, covering distance = a * 1 = a miles

Distance left to travel = (D - a) miles

After 1 hour both trains are traveling towards each other & meet each other after 1 hour,

Hence we have, (D - a) = 2a * 1 = 2a

D = 3a or D/a = 3

Hence Statement 1 alone is Sufficient.

Statement 2:

Train B travels at the rate of 150 miles per hour.

Hence a = 150 miles per hour, but no information about the distance traveled.

Statement 2 alone is Not Sufficient.

Answer A.

Thanks,

GyM

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