Question 998845: A salmon wims 100 m in 8 min downstream. Upstream, it would take the fish 20 min to swim the same distance. What is the rate of the salmon in still water? What is the rate of the current?
Answer by ikleyn(52873)   (Show Source):
You can put this solution on YOUR website! .
A salmon wims 100 m in 8 min downstream. Upstream, it would take the fish 20 min to swim the same distance.
What is the rate of the salmon in still water? What is the rate of the current?
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Downstream, the salmon's speed relative to the river banks is  = 12.5  .
This speed is the sum of the salmon's speed relative water, u, and the speed of current, v:
12.5 = u + v. (1)
Upstream, the salmon's speed relative to the river banks is  = 5 .
This speed is the difference of the salmon's speed relative water, u, and the speed of current, v:
5 = u - v. (2)
Add (1) and (2). You will get
2u = 12.5 + 5 = 17.5, hence, u =  = 8.75 .
Then v = 8.75 - 5 = 3.75 .
Answer. The salmon's speed in a still water is 8.75 .
The current speed is 3.75 .
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