SOLUTION: 1. Mike can row in still water at a speed twice that of the current in a certain river. It takes Mike 2 hours more to row 10 km up the river than it takes him to row 15 km down the

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Question 593007: 1. Mike can row in still water at a speed twice that of the current in a certain river. It takes Mike 2 hours more to row 10 km up the river than it takes him to row 15 km down the river. What is the speed of current in the river?



Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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1. Mike can row in still water at a speed twice that of the current in a certain river.
It takes Mike 2 hours more to row 10 km up the river than it takes him to row 15 km down the river.
What is the speed of current in the river?
:
Let r = speed of current of the river
It states, "row in still water at a speed twice that of the current", therefore
2r = his rowing speed in still water
Then
2r - r = r, effective speed upstream
2r + r = 3r, effective speed downstream
:
Write time equation
Upriver time - downriver time = 2 hrs
10%2Fr - 15%2F%283r%29 = 2
multiply by 3r
3r*10%2Fr - 3r*15%2F%283r%29 = 3r(2)
Cancel the denominators
3(10) - 15 = 6r
30 - 15 = 6r
15/6 = r
r = 2.5 km/hr is the speed of the current
:
:
Check that out, rowing speed in still water will be 5 km/hr, find the times
10/2.5 = 4hrs
15/7.5 = 2hrs
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difference: 2 hrs