Two trains start simultaneously from opposite ends of a 180-km route and travel toward each other on parallel tracks. Train X, traveling at a constant rate, completes the 180-km trip in 5 hours. Train Y, travelling at a constant rate, completes the 180-km trip in 4 hours. How many kilometers had Train X traveled when it met Train Y?	Choose the correct choice from the following options.
A) 72
B) 74
C) 76
D) 78
E) 80

Rationale: if the two trains cover a total distance d , then train x travels ( 4 / 9 ) * d while train y travels ( 5 / 9 ) * d . if the trains travel 180 km to the meeting point , then train x travels ( 4 / 9 ) * 180 = 80 km . the answer is e .
Answer: E