Question 890098
They are both moving away from the station.  This analysis will use time quantities and not time points.


The northbound train travels for 1 hour before the southbound train begins its travel.


________________speed_________time_________distance
north___________55____________t+1___________{{{55(t+1)}}}
south___________45_____________t____________{{{45*t}}}
TOTAL______________________________________275


The equation that can be written from that data table allows you to find how much time, t.
{{{55(t+1)+45t=275}}}
{{{5t+55+45t=275}}}
{{{50t=275-55}}}
{{{50t=220}}}
{{{5t=22}}}
{{{highlight(t=22/5=4&2/5)}}} hours.
This is 4 hours 24 minutes.