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.)
Bob first loses his hat 1 mile upstream, at which time the hat remains stationary relative to the water. Bob continues to move in the water at a constant speed, first for 5 minutes away from the hat, and then for another 5 minutes towards the hat, as Bob's speed in the water is constant and the hat is not moving relative to the water. During this 10 minutes, the hat along with the water has moved 1 mile. One mile in 10 minutes is 6 miles per hour.

Posted by Charlie
on 20030505 16:24:12 