SOLUTION: Ed can row 5 km downstream in half the time it takes him to row 5 km upstream. If the current is 2 km/hour, how fast can Ed row in still water.

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Question 1159231: Ed can row 5 km downstream in half the time it takes him to row 5 km upstream. If the current is 2 km/hour, how fast can Ed row in still water.
Answer by ikleyn(52776) About Me  (Show Source):
You can put this solution on YOUR website!
.

Let r be his rate in still water.


Then the rate downstream is (r+2) km/h; while the rate upstream is (r-2) km/h.


The time to travel 5 km downstream is  5%2F%28r%2B2%29;  The time to travel 5 kn upstream is  5%2F%28r-2%29.


Now your equation becomes


    5%2F%28r-2%29 = 2%2A%285%2F%28r%2B2%29%29.


To solve it, cross multiply


    5*(r+2) = 2*5*(r-2).


Simplify and solve

    5r + 10 = 10r - 20

    10 + 20 = 10r - 5r

    30      = 5r

     r      = 30/5 = 6.


ANSWER.  Ed's rate in still water is 6 km/h.

Solved.