SOLUTION: River is running at 2 km/h. It look a man twice as long to row up as to row down the river.the rate(in km/h)of the man in still water is?

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Question 872640: River is running at 2 km/h. It look a man twice as long to row up as to row down the river.the rate(in km/h)of the man in still water is?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
River is running at 2 km/h.
It look a man twice as long to row up as to row down the river.
the rate(in km/h)of the man in still water is?
:
let s = the rate in still water
then
(s+2) = effective speed down stream
and
(s-2) = effective speed up stream
:
let d = the one way distance
:
Write a time equation; time = dist/speed
time up = twice time down
d%2F%28%28s-2%29%29 = 2%28d%2F%28%28s%2B2%29%29%29
d%2F%28%28s-2%29%29 = %282d%29%2F%28%28s%2B2%29%29
cross multiply
2d(s-2) = d(s+2)
Divide both sides by d
2(s-2) = s + 2
2s - 4 = s + 2
2s - s = 2 + 4
s = 6 km/hr his rate in still water