SOLUTION: Joe leaves on a car trip,driving a steady 45 mph. He expects the trip to take exactly 3 hours. After he has been driving for an hour, he realizes he has forgotten an appointment, a

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Question 967014: Joe leaves on a car trip,driving a steady 45 mph. He expects the trip to take exactly 3 hours. After he has been driving for an hour, he realizes he has forgotten an appointment, and he needs to arrive a half hour earlier than planned. How many miles per hour will he need to drive for the rest of the trip to make his goal?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+d+=+r%2At+
+d%5B1%5D+=+45%2A3+
+d%5B1%5D+=+135+
The distance he needs to drive must
be 135 mi
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In +1+ hr, he drives
+d%5B2%5D+=+45%2A1+
+d%5B2%5D+=+45+ mi
------------------
The remaining distance he has to drive is:
+d%5B3%5D+=+d%5B1%5D+-+d%5B2%5D+
+d%5B3%5D+=+135+-+45+
+d%5B3%5D+=+90+
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He planned to drive for +3+-+1+=+2+ more hrs
He wants to drive for +2+-+.5+=+1.5+ hrs
+d%5B3%5D+=+r%2A1.5+
+90+=+r%2A1.5+
+r+=+90%2F1.5+
+r+=++60+
------------
He will need to drive +60+ mi/hr to
arrive 1/2 hr early