SOLUTION: A columbia river tugboat can go 12 mph in still water. It travels up the river 30 miles and back 30 miles in a total time of 6 hours. What is the speed of the current?

Question 618536: A columbia river tugboat can go 12 mph in still water. It travels up the river 30 miles and back 30 miles in a total time of 6 hours. What is the speed of the current?

Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
A Columbia river tugboat can go 12 mph in still water.
It travels up the river 30 miles and back 30 miles in a total time of 6 hours.
What is the speed of the current?
:
Let c = speed of the current
:
Write a time equation; time = dist/speed
:
Time downstream + Time up = 6 hrs
+ = 6
multiply by (12-c)(12+c), results:
30(12+c) + 30(12-c) = 6(12-c)(12+c)
360 + 30c + 360 - 30c = 6(144 - c^2)
720 = 864 - 6c^2
6c^2 = 864 - 720
6c^2 = 144
Divide both sides by 6
c^2 = 24
c =
c = 4.9 mph is the current
:
:
:
Check this:
+ = 6.00

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