SOLUTION: A motorist averaged 670 miles in 12 hours. Before 4 pm, he averaged 60 mph and after 4 pm he averaged 50 mph. At what time did he begin his trip and at what time did he end it?

Question 1014272: A motorist averaged 670 miles in 12 hours. Before 4 pm, he averaged 60 mph and after 4 pm he averaged 50 mph. At what time did he begin his trip and at what time did he end it?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = distance in miles he covered before 4 PM
= distance in miles he covered after 4 PM
Let = time of trip before 4 PM
= time of trip after 4 PM
--------------------------------
Equation before 4 PM:
(1)
Equation after 4 PM:
(2)
----------------------------
Substitute (1) into (2)
(2)
(2)
(2)
(2)
(2)
and

--------------
7 hrs before 4 PM is 9AM
5 hrs after 4 PM is 9 PM
----------------------
He began at 9AM and ended at 9 PM
--------------------------------
check:
(1)
(1)
(1)
and
(2)
(2)
(2)
(2)
(2)
OK
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