a train leaves a station and travels north at 85 km/hr. Four hours later, a second train leaves on a parrallel track and travels north at 125km/hr. How far from the station will they meet?

1 answer

Train #1 = t hrs.
Train #2 = (t-4)hrs.

When train #2 catches up, they would have traveled the same distance:

d1 = d2.
85t = 125(t-4),
85t = 125t - 500,
125t - 85t = 500,
40t = 500,
t = 12.5 hrs.

d = Vt = 85 * 12.5 = 1062.5km.