SOLUTION: Julie left her house and drove toward work at an average speed of 45 mi/h. Rob left some time later driving the same direction at an average speed of 60 mi/hr. After driving for 4

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Question 1086277: Julie left her house and drove toward work at an average speed of 45 mi/h. Rob left some time later driving the same direction at an average speed of 60 mi/hr. After driving for 4 hours Rob caught up with Julie. How long had Julie been driving when Rob caught up with Julie? (Round to the nearest tenth)
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +d%5B1%5D+ = Julie's head start in miles
Let +t%5B1%5D+ = Julie's head start in hrs
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Start a stop watch when Rob leaves
Let +d+ = distance in miles that Rob travels
until he catches up with Julie
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Rob's equation:
(1) +d+=+60%2A4+
Julie's equation:
(2) +d+-+d%5B1%5D+=+45%2A4+
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Plug (1) into (2)
(2) +240+-+d%5B1%5D+=+180+
(2) +d%5B1%5D+=+60+
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How much is Julie's head start in hours?
+d%5B1%5D+=+45%2At%5B1%5D+
+60+=+45%2At%5B1%5D+
+t%5B1%5D+=+4%2F3+ hrs
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Then Julies drives for +4+ more hrs, so
+4%2F3+%2B+4+=+5+%2B+1%2F3+
Convert +1%2F3+ hrs to minutes
+%281%2F3%29%2A60+=+20+ min
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Julie had been driving for 5 hrs and 20 min
when Rob caught up with her