SOLUTION: A train leaves Dallas and travels north at 85 kilometers per hour. Another train leaves at the same time and travels south at 70 kilometers per hour. How long will it take before t

Question 959050: A train leaves Dallas and travels north at 85 kilometers per hour. Another train leaves at the same time and travels south at 70 kilometers per hour. How long will it take before they are 620 kilometers apart?
How do I solve this problem?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
You can think of this a one train ( either one )
moving at the sum of their speeds, and the
other train standing still
-------------------------
Let = time in hours when they are
km apart
-------------------

In 4 hrs they will be 620 km apart
----------------
check:
Equation for southbound train:

Equation for northbound train:

-----------------

OK
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