let's look at the difference in speed between the two: it's 39-15.6=23.4 km/h
(we can just subtract this because they are traveling in the same direction) - this means that it's as if the slower train (the freight) was in place and the passenger train was traveling at 23.4 km/h
No, the freighter left 3.9 hours earlier, during which it traveled
15.6*3.9=60.84 km
So they will meet when the passenger train will catch up on those 60.84 km.
It does it with 23.4 km/h so it will need:
\(\frac{6084}{2340} =2.6\)
So the freighter will be travellinf for 2.6 more hours than the other train - a total of (2.6+3.9=6.5) 6.5 hours!
