SOLUTION: A certain river has a current of 3kph. A boat takes twice as long to travel upstream between two points. As it does to travel downstream between the same two points. What is the sp

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Question 540824: A certain river has a current of 3kph. A boat takes twice as long to travel upstream between two points. As it does to travel downstream between the same two points. What is the speed of the boat in still water?
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
Let the speed of the boat in still water be x.
The speed of the boat upstream (in kph) is x-3
The speed of the boat downstream (in kph) is x+3
and we know its twice as fast as when going upstream, so
x+3=2(x-3) --> x+3=2x-6
subtracting x from both sides we get
3=x-6
adding 6 to both sides we get 9=x, or more conventionally written
x=9
The speed of the boat in still water is 9 kph.