SOLUTION: Please help me with this word problem! I've been trying it for about 30 minutes and can't seem to figure it out. A boat went 8 kilometers upstream and returned all in two hours

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Question 1004729: Please help me with this word problem! I've been trying it for about 30 minutes and can't seem to figure it out.
A boat went 8 kilometers upstream and returned all in two hours. If the current was running at 3 km/hr, what is the boat's speed in still water.

Thank you so much!
Answer by ikleyn(52794) (Show Source):
You can put this solution on YOUR website!
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A boat went 8 kilometers upstream and returned all in two hours. If the current was running at 3 km/hr, what is the boat's speed in still water.
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Let u be the boat's speed in still water in .
Then the boat's speed relative to the river's bank is (u-3) upstream and (u+3) downstream.

The time the boat spent for the upstream trip is hours.
The time the boat spent for the downstream trip is hours.

So, you have an equation for the duration of the close loop trip:

+ = 2.

Solve it. The first step is to multiply both sides by (u-3)*(u+3).

Answer. 9 .