[Fsf-friends] Four Friends - Part I

[Ramanraj K]

On 8/7/05, Anand Babu <ab@gnu.org.in> wrote:
> ,----[ Ramanraj K <ramanraj.k@gmail.com> ]
> | Arvind, an old friend of mine, recently told me this story:
> |
> | One night, four travellers named One, Two, Five and Ten walking
> | through a forest, come to a deep gorge and find that they have to
> | continue their journey across a weak wooden bridge, that won't stand
> | the weight of more than any two of them at a time.  The bridge has a
> | few missing logs and they had only one torch with them to guide them
> | across. Also, One takes 1 minute, Two takes 2 minutes, Five takes 5
> | minutes and Ten takes 10 minutes to cross the bridge, due to their
> | individual abilities.  What is the minimum time within which the
> | four friends could cross the bridge?
> |
> | I reasoned that One being the fastest, could take Two, Five and Ten
> | across in about 19 minutes as follows:
> |
> | Task                             ::: Time taken in minutes
> | ----------------------------------------------------------
> | 1 and 10 take torch and walk across: 10
> | 1 returns with torch               :  1
> | 1 and 5 walk across with the torch :  5
> | 1 returns  with torch              :  1
> | 1 and 2 cross with the torch       :  2
> | ----------------------------------------------------------
> | Total time:                      ::: 19 minutes
> |
> | Arvind said that they could save two minutes with another plan.  I
> | was sure there is a "catch" somewhere, because it appeared
> | impossible.  Did 1 and 2 cross earlier, and did 2 throw the torch
> | from the other side?  No, there are no catches, it is a purely
> | logical problem to be solved just the way I proposed, but his plan
> | would take two minutes less of time. How could they cross the bridge
> | in just 17 minutes?
> `----
> 
>  Task                             ::: Time taken in minutes
>  ----------------------------------------------------------
>  1 and 2  take torch and walk across : 2
>  1 returns with torch                : 1
>  10 and 5 walk across with the torch : 10
>  2 returns  with torch               : 2
>  1 and 2 cross with the torch        : 2
>  ----------------------------------------------------------
>  Total time:                      ::: 17 minutes

AB, I am not surprised that you solved this :) 

We could replace the elements in the story with modems. data packets,
bandwidth; fuel, cars, trips; developers, users, project goals, free
software development and highlight the importance of distributing
resources in an intelligent manner.

Though One is the fastest, if he were asked to do all the work he
would get tired too soon, but with good distribution, we can save
time, conserve resources, and achieve goals with efficiency.

Happy hacking :)

-Ramanraj.