SOLUTION: A fisherman can row up stream at 2mph and downstream at 8mph. He started rowing upstream until he got tired and then he rowed down stream to his starting point. How far did her row

Question 468359: A fisherman can row up stream at 2mph and downstream at 8mph. He started rowing upstream until he got tired and then he rowed down stream to his starting point. How far did her row if the entire trip took 2 hours?
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
d = rt
t = d/r
2 = d/2 + d/8 = 5d/8
5d = 16
d = 3.2 miles one way
--> 6.4 miles total
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Another approach:
The average speed of a round trip is
2*v1*v2/(v1 + v2)
2*2*8/(2+8) = 3.2 mph
It's similar to parallel resistors, but 2 times that.
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His avg speed was 3.2 mph for 2 hours = 6.4 miles round trip

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