SOLUTION: A boat travelling upstream goes 84 kilometers in 7 hours. If the return trip takes only 3 hours, what is the speed (in kilometers per hour) of the boat in still water?

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Question 1155687: A boat travelling upstream goes 84 kilometers in 7 hours. If the return trip takes only 3 hours, what is the speed (in kilometers per hour) of the boat in still water?

Found 2 solutions by Boreal, Alan3354:
Answer by Boreal(15235) (Show Source):
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current is c
speed is s
distance=s*time
it goes upstream (s-c)=12 km/h
it goes downstream (s+c)=28 km/h (84/3)
therefore,
s-c=12
s+c=28
2s=40
s=20 km/h ANSWER
c=8 km/h

Answer by Alan3354(69443) (Show Source):
You can put this solution on YOUR website!
A boat travelling upstream goes 84 kilometers in 7 hours. If the return trip takes only 3 hours, what is the speed (in kilometers per hour) of the boat in still water?
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Find the 2 speeds, upstream and downstream.
The boat's speed is the average of the 2.
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The speed of the current is the difference between boat speed and either speed, up or down stream.