Re: [Paddlewise] You do the math.......

Sidney_Stone_at_amsinc.com wrote:
> 
> ...
> The answer to Question 2 is 4.8 hours (4 hours 48 minutes).  Here's the
> math:
> 
> ...<snip>...
>
> 6 miles divided by 1.25 mph = 4.8 hours
> 

Sidney, this last step is where you made your mistake--misapplying the
1.25 mph average. The average speed of 1.25 mph only applies to a full
cycle of "paddle forward-drift back". On the last cycle you reach your
destination prior to the "drift back" portion of the cycle (thus raising
the average speed for the last portion of the journey). This can be seen
as follows:

After 4 hours at the average speed of 1.25 mph, you will have gone 5
miles, one mile short of your destination. At this point you will
complete two additional paddle-forward-and-drift-back cycles, which will
take 40 minutes and move you 10/12 mile, leaving you 2/12ths of a mile
short. As you begin the last cycle you paddle forward at a net speed of
2 mph, and thus complete the final 2/12ths of a mile in 5 minutes (for a
total time of 4 hours and 45 minutes).  Since this last leg only takes 5
minutes of paddling, you arrive prior to the final "drift back" portion
of the cycle. For the last 2/12ths of a mile you are averaging 2 mph,
not 1.25 mph (as your calculation assumes).

I hope that this clears things up.

Dan Hagen
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