Two trains leave the same station. At what time exactly will they meet?

Question

Two trains leave the same station, the first one at 1.00pm with speed 40mph and the second one, 45 minutes later, with speed 55mph. At what time exactly will they meet?

Answer 1

After "t" hours, train one has travelled 40mph * t

At the same time, train two has been traveling for t-0.75 hours (since it left 45 minutes = 0.75 hours later) and has travelled 55mph * (t-0.75)

 

Want the time when they're equal: 40t = 55(t-0.75)

                                                   15t = 0.75*55

                                                   t-0.75*55/15 = 2.75 hours.  

t represents the time, after 1pm. 2.75 hours after this is 3:45pm