SOLUTION: Sandy can swim 1 mile upstream in 20 minutes. She can swim the same distance downstream in 9 minutes. Find the speed of the current and of Sandy if both stay constant.

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Question 251327: Sandy can swim 1 mile upstream in 20 minutes. She can swim the same distance downstream in 9 minutes. Find the speed of the current and of Sandy if both stay constant.
Answer by solver91311(24713)   (Show Source): You can put this solution on YOUR website!


Let represent her speed in still water and let represent the speed of the current.

Since we know that distance equals rate times time, 20 minutes is one-third of an hour, 9 minutes is 3/20ths of an hour, her speed relative to dry land upstream (against the current) must be , and the speed downstream must be , we can say the following things:

With respect to the upstream trip:



And with respect to the downstream trip:



A little arithmetic:





Now all you need to do is solve the linear system. The coordinates of the single ordered pair in the solution set are the answers you seek.

John
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