SOLUTION: A train leaves Little​ Rock, Arkansas, and travels north at 90 kilometers per hour. Another train leaves at the same time and travels south at 80 kilometers per hour. How long wi

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Question 1136344: A train leaves Little​ Rock, Arkansas, and travels north at 90 kilometers per hour. Another train leaves at the same time and travels south at 80 kilometers per hour. How long will it take before they are 680 kilometers​ apart?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of travel
Let +t+ = time in hrs
+680+=+%28+90+%2B+80+%29%2At+
+680+=+170t+
+t+=+4+
In 4 hrs they are 680 km apart
-------------------------------------
check:
+d%5B1%5D+=+90%2A4+
+d%5B1%5D+=+360+
and
+d%5B2%5D+=+80%2A4+
+d%5B2%5D+=+320+
and
+d%5B1%5D+%2B+d%5B2%5D+=+360+%2B+320+
+d%5B1%5D+%2B+d%5B2%5D+=+680+
OK