Bob is having a nice camping/fishing trip along a river. He leaves his campsite early in the morning, and gets on his boat, heading full throttle upstream.

After going for exactly one mile, his hat flips off of his head, and starts floating downstream. Bob doesn't realize that his hat has fallen off for five minutes, but then he notices that it's missing, and turns full throttle downstream.

He finally catches the hat at exactly the same spot as he camped that morning. The question is, how fast was the water traveling?

(Assume that he travels the same speed the entire time and that there is no turn around time.)

The general formula for solving these type of problems is :

Speed of the water = d / (2 * t) miles/minute

Where d = distance travelled by the hat
t = time travelled upstream in minutes without noticing the fallen hat

In our present case, d = 1 mile, t = 5 minutes.

Hence Speed of the Water = 1 / (2 * 5) = 1/10 = 0.1 miles/minute or 0.1*60 = 6 miles per hour.

Posted by Jayaram S on 2003-05-07 00:14:54