Los Angeles, CA and Charleston, SC are separated by 3500 km. A train carrying cats leaves Charleston, SC at 12:30p heading west at an average speed of 130 km/hr. At 5:45p, a train carrying TNT leaves LA heading east at 90 km/hr. From the time the Los Angeles train left the station, how many hours did it take before it collides with the South Carolina train?
By 5:45 pm, the LA train has been going for 5.25 hours, and has covered 682.5 km
So, the trains are then 2817.5 km apart
Since their combined speed is 220 km/hr, it will take another 12.8 hours till they meet
5.25 + 12.8 = 18.05 hours