SOLUTION: P and Q are two stations. Train A started from P towards Q at 6:00 a.m at 90 kmph. At the same time, train B started from R, an intermediate station 60 km from P, and travel

Let t be the time train A traveled to get the meeting point (in hours).


     Then from the problem, train B traveled the same time t from R to get the meeting point;
                            train C traveled (t-1) hours from Q to get the meeting point.

 
Consider trains A and B.

     To get the meeting point, train A traveled 90*t kilometers;
                               train B traveled 60*t kilometers.

     For train B, the travel distance to get the meeting point was 60 km less than that for train A, 
     so we write this equation

          90t = 60t + 60.


We simplify this equation and find t

          90t - 60t = 60

           30t = 60

             t = 60/30 = 2 hours.


Now we know that the travel time for A to get the meeting point was 2 hours;
hence, the travel time for train C was 1 hour less that that, or 2-1 = 1 hour.


At this point, we can find the total distance PQ.  It is the sum of partial distances 
for train A and train C to get the meeting point, or

    90*2 + 120*1 = 180 + 120 = 300 kilometers.


ANSWER.  The distance from P to Q is 300 kilometers.