How Long for Two Trains to Pass Each Other?

[P6nub]

Homework Statement

A 120m long train with a constant speed of 10.0m/s is passing by a 80.0m long train traveling at 6.0m/s on the opposite lane. How long does it take for these two train to completely pass by each other if their distance in between is 260m?

Homework Equations

v=d/t

The Attempt at a Solution

Total distance Train A has to cover: 260m+80m= 340m
Total distance Train B has to cover: 260m+120m= 380m

Train A's Time = 340m / 10m/s
= 34s

Train B's Time = 380m / 6m/s
= 63.33s

Then I am not sure what to do next but I'm given the answer of 28.8s...

 

[Delphi51]

Welcome to PF!

Total distance Train A has to cover: 260m+80m= 340m

Curious wording here. It WILL cover some distance while the pass is happening, and how far that is will depend on how long it takes the other train to go by. So, your formula for the distance traveled by train A should have a T for time in it. You know its speed, so you should be able to write an expression for how far it goes in time T. I wouldn't add any length or closing distance onto that. The final equation will go something like this:
distance traveled by train B in time T = separation + length + distance traveled by train A in time T.

Note the T's in the equation - you will be able to solve the equation for the time and get the answer to the question.