Look Down Below For question:

The cattle train
speed - 36.5 km/h
time - x h

the passenger train
speed - 29.2 km/h
time - (2.4+x) h

The cattle train caught up to the passenger train so the distance they travelled is the same.
Distance is speed times time.



The passenger train travelled for 12 hours before the cattle train caught up.

Used brute force to figure this one out and got lucky at t=12.

What you need to know:



t = time travelled (in hours)

x = distance passenger train has travelled

y = distance cattle train has travelled

d = distance between both trains in km

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RESULTS AND TIME SNAPSHOTS:

When:

t=0, x=0, y=0, d=0

t=2.4, x=70.08, y=0, d=70.08

t=4.8, x=140.16, y=87.6, d=52.56

t=7.2, x=210.24, y=175.2, d=35.04

t=9.6, x=280.32, y=262.8, d=17.52

t=12, x=350.4, y=350.4, d=0 <-------

So your answer is 12 hours.