SOLUTION: A man rowed up a river of 1 kilometer in 6hours and back in 4 hours. Find the rate of the current and his rate of rowing in still water.

Let u be the rate of rowing, in km/h, and 

let v be the rate of the current.


Then from the condition you have


    u + v =     (1)    (the speed moving downstream)

    u - c =     (2)    (the speed mowing upstream)


Add the equations to get

    2u =  +  =  +  = ,

     u =  kilometer per hour.


Then from (1)  v =  -  =  -  = .


ANSWER.  Rate of rowing in still water is  km/h.


         Rate of the current is  km/h.