Answer:
Train B catches up with train A at 2.25 h
The two trains meet at 108 Km from the start
Explanation:
Relative Speed
There are two trains, A and B leaving the same station. Train A leaves 45 minutes before train B at va=36 Km/h. Train B travels at vb=48 Km/h in the same direction, so they eventually meet.
i)
Calculate the head start of train A Xh, i.e. the distance it traveled in 45 minutes = 45/60=0.75 h.
When train A is 27 Km ahead, train B leaves the station. The relative speed between them is vb-ba=48 - 36 = 12 Km/h.
Thus, for train B to meet with train A, the head start must be traveled at the relative speed.
The time needed to do that is:
t = 2.25 h
Train B catches up with train A at 2.25 h
ii) In the time calculated above, train B has traveled a distance of:
The two trains meet at 108 Km from the start