Question 362839: Kim averaged 52mph on state highways and 62mph on interstate highways on a 450-mile trip. if her driving time was 7 hours-45 minutes, how many hours did she spend on state highways? assume that the entire 7 hours-45 minutes was spent on either state or interstate highways, and round your answer to the nearest tenth of an hour
Answer by robertb(5830)   (Show Source):
You can put this solution on YOUR website! Let s = # hours on state h-way, i = # hours on interstate h-way. Then
 .
From the top equation, s = 7.75 - i. Sustitute into the bottom equation,
we get
52(7.75-i)+62i = 450,
403 -52i+62i = 450,
10i = 47,
i = 4.7, and s = 7.75 - 4.7 = 3.05.
Therefore kim spent 4.7 hours in interstate h-way, and 3.05 hours in state h-ways.
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