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# Physics word problem - trains

Sun 6 Jan, 2013 11:30 am
There are two cities (A and B). On a train from A to B, every 50 minutes the train meets another train going in the opposite direction (from B to A), on a parallel track. Constant speed of the train(A to B) is 90 km/hr and the speed of all approaching trains is 120km/hr (B to A). Someone assumes that the approaching trains leave her home town at regular intervals and travel at constant speed, and is able to calculate the time period between their departures. Duplicate her calculations (answer in minutes)
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View best answer, chosen by greatestever298

1
Sun 6 Jan, 2013 12:02 pm
@greatestever298,
I get 87.5 minutes apart.
greatestever298

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Sun 6 Jan, 2013 12:09 pm
How did you get that, can you post the solution, thats the right answer.

2
Sun 6 Jan, 2013 01:55 pm
@greatestever298,
The trains pass every 50 minutes, so the distance between the BA trains can be calculated using the combined speeds of the AB and BA trains.

Then you can calculate the time between trains, by using the speed of BA train, and the distance between the BA trains.
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