Posted by JD on Thursday, July 31, 2014 at 3:27pm.
Two trains, one starting in Calgary and the other in Edmonton, travel toward one another. The Edmonton train travels at 120 km/h toward Calgary, while the Calgary train travels at 140 km/h toward Edmonton. If the trains begin at the same time and Edmonton and Calgary are 285 km apart, how far from Calgary will the trains pass each other? (153 km)

Physics  bobpursley, Thursday, July 31, 2014 at 3:30pm
time to crash: distance/velocity=153km/260km/hr=.588hr
distance from calagary: 140*.588 km 
Physics  Steve, Thursday, July 31, 2014 at 5:04pm
The trains approach at 260km/hr
The distance to cover is 285km. So, it takes 285/260 hrs to meet.
In that time, the train from Calgary covers 285/260 * 140 = 153 km