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Rate of speed question. ( Rowing with and against current )?
I came across this word problem in workbook and I can't seem to figure out where to begin. It goes :
A canoeist's rate of speed in still water is 8 miles per hour. If he can travel 60 miles upstream and 60 miles downstream in a total of 16 hours, what is the rate of the current?
I have no idea where to begin with this :( .
3 Answers
- Don E KnowsLv 61 decade agoFavorite Answer
The current is 2 MPH.
You need to find 2 numbers such that :
(8 - x) t = (8+ x)(16 - t)
I found that 2 works here by an educated guess.
(8 - 2) 10 = (8 + 2) 6
and 10 + 6 = 16
- 1 decade ago
Well to start you already now the speed the canoist can travel in still water! This should help you. Now, immagine your self in a pool... there you would have a speed in still water (top speed). Now imagine you go into a river and you try to swim down-stream (with the current). The speed that someone at the shore will see you swimming will be your speed (top speed) + the speed of the current, since it is pushing you faster. This 'total' speed (with current) is what you will need to use to compute distances. In the event that you will be swimming against the stream then the current will slow you down: your speed - speed of current. This 'total' speed (counter-current) will be used to compute distances.
You can start considering the trip up-stream and then the trip down-stream. Also, distance up = speed up. time up. Or distance down = speed down. time down. These speeds will refer to the 'total' speed on each leg.
Hope this helps. Good luck!
Source(s): Experience - .Lv 61 decade ago
Not enough information to solve. How far did he get going up stream and in what portion of the 16 hours did it take. Then you could compute the current. As it stands, he could have done it on calm water, but we do not know the other variables.