SOLUTION: if you are rowing a boat at 40 miles an hour for 4 hours down stream and then 40 miles per hour back up stream for 10 hours what is the current

Question 286064: if you are rowing a boat at 40 miles an hour for 4 hours down stream and then 40 miles per hour back up stream for 10 hours what is the current
Answer by Earlsdon(6294) (Show Source): You can put this solution on YOUR website!
Use the formula:
where: d = distance, r = rate(speed), and t = time of travel.
In this problem, the distance, d, is the same for the downstream trip and the upstream trip, so...
For the downstream trip, the speed of the boat relative to the shore equals the boat speed on the water plus the speed of the current, so we'll let r = the boat speed and S = the speed of the current.
Substitute r = 40 mph and t = 4 hrs.
Simplify.

For the upstream trip, let r = the boat speed and S = the speed of the current.

Simplify.
But the distances are equal, so...
then...
Add 10S to both sides.
Subtract 160 from both sides.
Divide both sides by 14.

The speed of the current is 17.146 mph.
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