Two trains 45 km away from each other running on parallel ra

Two trains, 45 km away from each other, running on parallel railroad tracks, approach each other traveling at constant speed of 12 m/s and 18 m/s respectively. How long will it take before the trains meet?

Solution

This your classic RTD problem. Let\'s set up the rtd table. First notice that the units of length are not the same 45 km = 45,000 m
label . . . rate . . . time . . . distance
T1 . . . . 12 . . . . t . . . . . 12t
T2 . . . . 18 . . . . t . . . . . 18t
total . . . . . . . . 2t . . . . .45000
Now 30t = 45,000 - - > t = 15,000 sec = 250 minutes or 4hr 10 min.