SOLUTION: A boat traveled downstream a distance of 85 mi and then came right back. If the speed of the current was 8 mph and the total trip took 5 hours and 40 minutes, find the average spee

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Question 1066481: A boat traveled downstream a distance of 85 mi and then came right back. If the speed of the current was 8 mph and the total trip took 5 hours and 40 minutes, find the average speed of the boat relative to the water.
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
         SPEED        TIME              DISTANCE

DOWN        r+8       85%2F%28r%2B8%29             85

UP          r-8       85%2F%28r-8%29             85

Total                5%262%2F3


85%2F%28r%2B8%29%2B85%2F%28r-8%29=5%262%2F3
Solve this for r.