Online Word Problems #18

[Carla]

I would like to go over statement (2) for this example.

[Guest]

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.

[StaceyKoprince]

Statement 2 alone:

If train B = 150 mph, then train A = 150 mph b/c the question tells us that the two trains travel at the same rate. The question also tells us that A passes B after A has been traveling for two hours. If A has traveled for 2 hours, A has gone 300 miles. But I don't know if A and B started at the same time (in which case they have both traveled 300 miles and the total distance would be 600, so it would take B 4 hours to go the whole way) or if B started, say, half an hour ago (in which case A has traveled 300 miles but B has traveled only 75 miles and the total distance would be 375, so it would take B 2.5 hours to go the whole way).

You might have assumed that they both started at the same time - but the problem doesn't actually say that. Assume nothing on data sufficiency!

[unique]

Statement 2 alone:

If train B = 150 mph, then train A = 150 mph b/c the question tells us that the two trains travel at the same rate. The question also tells us that A passes B after A has been traveling for two hours. If A has traveled for 2 hours, A has gone 300 miles. But I don't know if A and B started at the same time (in which case they have both traveled 300 miles and the total distance would be 600, so it would take B 4 hours to go the whole way) or if B started, say, half an hour ago (in which case A has traveled 300 miles but B has traveled only 75 miles and the total distance would be 375, so it would take B 2.5 hours to go the whole way).

You might have assumed that they both started at the same time - but the problem doesn't actually say that. Assume nothing on data sufficiency!

Is the answer C?

[StaceyKoprince]

Correct answer is A. I won't say anything else yet - see if you can figure it out on your own.