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Subj:.....Hat In The River (S255, S653) 
          From: LABLaughs.com on 12/17/2001 
Photo from DailyCal.org...
The Harvard bridge and the Longfellow bridge are 1 mile 
apart.  The MIT crew team starts rowing upstream at the 
Longfellow.  As the crew passes under the Harvard, the 
coxswain's hat falls into the river.  10 minutes later, the 
coxswain notices and turns the boat around instantaneously 
and has the crew go back to get it, rowing at the same 
constant rate.  By the time the team reaches the hat, they 
are back at the Longfellow.  How fast is the river flowing? 

Finger pointing down
from darrell94590 on 1/2/2006
Drawing from Ripleys-Believe It Or Not

                  THE SOLUTION

Since the crew's speed is measured relative to the river and 
the hat is floating on the river, the time it takes the crew 
to get back to the hat is also 10 minutes. So, in 20 minutes 
the hat travelled 1 mile down the river. Therefore the river's 
speed is 1 mile/20 minutes or 3 miles per hour.