helpneeded105: Train A leaves San Francisco at 8 am and heads towards Los Angeles, travelling 55 km/h. At the same time, train B leaves Los Angeles and heads towards San Francsico, travelling 65km/h. The distance between the two cities is 230 km. At what time will they pass each other?
hi 105,
You have yourself a good question here!
.................................. .............................................................230km..........55km/hr
.................................. San F -------distance=d------------------------------X-------------------------------------------------------------------------> Los Angeles
.................................. .............................................................230km..........65km/hr
.................................. San F <--------------------------------------------------X-----------------distance = d
2 = (230 - d)------------------------ Los Angeles
X is the point where the trains pass.
now, speed = distance/time
so, time = distance/speed
We need to know how long it will take them to get to X. We know that they will both take the same amount of time. Let the time taken be t
For the top train: t = d/55
For the bottom train: t = (230 - d)/65
therefore
d/55 = (230 - d)/65
After solving this we get d = 105 and 5/12 km This is the distance the top train has travelled
230 - 105 and 5/12 = 124 and 7/12 km This is the distance the bottom train has travelled.
Now, distance/speed = time
Top train: [105 and 5/12] / 55 = 1 and 11/12 hours = 1 hour and 55 minutes
Bottom train: [124 and 7/12] / 65 = 1 and 11/12 hours = 1 hour and 55 minutes
Good they have both taken the same amount of time to get to this point.
8am + 1hour and 55min = 9:55am
The trains will pass each other at 9:55am
+118654 
