SOLUTION: a sailor sails a distance of 48 km along the flow of a river in 8 hr . if it take 12 hr to return the same distance , then the speed of the river is ?

Question 715565: a sailor sails a distance of 48 km along the flow of a river in 8 hr . if it take 12 hr to return the same distance , then the speed of the river is ?
Answer by DrBeeee(684) (Show Source): You can put this solution on YOUR website!
Let s = the speed of the boat
Let r = speed of the river
When traveling with the river the sailor travels 48km in 8hr, then we have
(1) s + r = 48/8 or
(2) s + r = 6
When going up the river he travels 48km in 12hr, then we have
(3) s - r = 48/12 or
(4) s - r = 4
Add (2) and (4) and get
(5) 2*s = 10 or
(6) s = 5
Use (6) in (2) and get
(7) 5 + r = 6 or
(8) r = 1
Let's check the answers with (4).
Is (5 - 1 = 4)?
Is (4 = 4)? Yes
Answer: The river is flowing at 1km/hr.
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