Railway track puzzle
m.c...@ic.ac.uk
This is a puzzle I enjoyed many years ago, way before the internet
was born. I cannot remember who the originator is, hence unable to
attribute the source.
1. A railway track has a depot, in which is an engine E, and two
stations A and B, each containing a coach, A and B, respectively.
2. The track passes through a bridge B which is wide enough for
coaches but not for the engine.
3. The engine can couple with coaches at the front and/or back.
4. A coach can be coupled to another coach.
4. The engine can travel forwards or backwards but obviously not able
to turn through acute angles.
Puzzle: How can the engine be used to transfer coach A from station A
to station B and coach B from station B to station A and then be
returned to the depot?
B
\___/
____________
/ ___ \
/ / \ \
/ \
/ \
_ | | _
| || || |
A |_|| ||_|B
| |
\ /|
\ / |
\ / |
\_____________/ |
|
|
|
_|_
| E |
|___|
Dale Johannesen
In article <4tq5p6$c...@sjsun1.cc.ic.ac.uk>, m.c...@ic.ac.uk writes:
|> This is a puzzle I enjoyed many years ago, way before the internet
|> was born. I cannot remember who the originator is, hence unable to
|> attribute the source.
|>
|>
|> 1. A railway track has a depot, in which is an engine E, and two
|> stations A and B, each containing a coach, A and B, respectively.
|> 2. The track passes through a bridge B which is wide enough for
|> coaches but not for the engine.
|> 3. The engine can couple with coaches at the front and/or back.
|> 4. A coach can be coupled to another coach.
|> 4. The engine can travel forwards or backwards but obviously not able
|> to turn through acute angles.
|>
|> Puzzle: How can the engine be used to transfer coach A from station A
|> to station B and coach B from station B to station A and then be
|> returned to the depot?
Simple. Delegate the problem to the idiot who built a railroad
bridge that wasn't wide enough for the engine.
Dennis Yelle
In article <4tq5p6$c...@sjsun1.cc.ic.ac.uk> m.c...@ic.ac.uk writes:
>
>1. A railway track has a depot, in which is an engine E, and two
>stations A and B, each containing a coach, A and B, respectively.
>2. The track passes through a bridge B which is wide enough for
>coaches but not for the engine.
>3. The engine can couple with coaches at the front and/or back.
>4. A coach can be coupled to another coach.
>4. The engine can travel forwards or backwards but obviously not able
>to turn through acute angles.
>
>Puzzle: How can the engine be used to transfer coach A from station A
>to station B and coach B from station B to station A and then be
>returned to the depot?
>
>
>
> \___/
> ____________
> / ___ \
> / / \ \
> / \
> / \
> _ | | _
> | || || |
> A |_|| ||_|B
> | |
> \ /|
> \ / |
> \ / |
> \_____________/ |
> |
> |
> |
> _|_
> | E |
> |___|
>
>
>
Hint:
The solution is straightforward, that is, there is nothing
tricky in the solution like switching the switch while the
train is moving over it, or hitting a car with enough force
to cause it to move from one station to another.
But, we do assume that the bridge is short enough for us to
leave a single car there, and come back on the other end
to pick it up.
Answer:
Station A Bridge Station B Spir
(left to right) (top to bottom)
---------------------------------------------------------------
A B E
A BE
B EA
EB A
EBA
EBA
B AE
B A E
--
den...@netcom.com (Dennis Yelle)
"You must do the thing you think you cannot do." -- Eleanor Roosevelt
Mathew Hendry
m.c...@ic.ac.uk wrote:
: This is a puzzle I enjoyed many years ago, way before the internet
: was born. I cannot remember who the originator is, hence unable to
: attribute the source.
: 1. A railway track has a depot, in which is an engine E, and two
:
:
:
:
:
SPOYLAH!
Neat puzzle. See if you can follow this ;)
Go to station B and couple with coach B. Push it towards and under the bridge
as far as is possible, then decouple from it. Go to station A and couple with
coach A. Push coach A towards and under the bridge, and couple coach B to it.
Pull both coaches around to station B, push them into the depot, then decouple
coach B from coach A. Pull coach A to station B, push it a short distance
towards station A, then decouple from it. Go to station B, back into the
depot, and couple with coach B. Pull coach B to station B, then push it
towards station A until it meets coach A. Couple coach A to coach B, and push
them both towards and under the bridge. Decouple coach A from coach B, pull
coach B to station A, and decouple from it. Go through station B to the
bridge, and couple with coach A. Pull it into station B, decouple from it, and
return to the depot.
-- Mat.
Tom Maciukenas
In article <4tq5p6$c...@sjsun1.cc.ic.ac.uk>, <m.c...@ic.ac.uk> wrote:
>This is a puzzle I enjoyed many years ago, way before the internet
>was born. I cannot remember who the originator is, hence unable to
>attribute the source.
>
>
>1. A railway track has a depot, in which is an engine E, and two
>stations A and B, each containing a coach, A and B, respectively.
>2. The track passes through a bridge B which is wide enough for
>coaches but not for the engine.
>3. The engine can couple with coaches at the front and/or back.
>4. A coach can be coupled to another coach.
>4. The engine can travel forwards or backwards but obviously not able
>to turn through acute angles.
>
>Puzzle: How can the engine be used to transfer coach A from station A
>to station B and coach B from station B to station A and then be
>returned to the depot?
Cool puzzle! Solution (sort of) below:
First, here's a mini version of the diagram:
Bridge
_-_
/ - \
A | | B
\___/|
|
|
E
Ok, engine E moves up, couples with coach B, and pushes it to the
bridge. It then goes into reverse, and accelerates as hard as it
can. Just before reaching the junction, it decouples, accelerates
a bit more, and takes the track back to the depot. Then before B
reaches the junction the engineer shoots the switch control so
that B coasts down the track toward A. This shall be termed
"High-Speed Maneuver #1".
Then, the train comes back and hooks up with B, and couples B to
A. It then pushes A as far as it can through the bridge, decouples
it from B, pulls B to station A, then goes around the circle, hooks
up with A from the other side, pulls it to station B, decouples,
and goes back to the depot.
QED :^)
If the engineer is too much of a safety-conscious wimp [ :^p ] to
perform High-Speed Maneuver #1 then boy I don't know what to tell
you!
-Tomm (Hopefully I'll come up with a real solution soon!)
Michael Chew
to...@dvorak.amd.com (Tom Maciukenas) wrote:
>In article <4tq5p6$c...@sjsun1.cc.ic.ac.uk>, <m.c...@ic.ac.uk> wrote:
>>This is a puzzle I enjoyed many years ago, way before the internet
>>was born. I cannot remember who the originator is, hence unable to
>>attribute the source.
>>
>>
>>1. A railway track has a depot, in which is an engine E, and two
>>stations A and B, each containing a coach, A and B, respectively.
>>2. The track passes through a bridge which is wide enough for
>QED :^)
Hi Tom,
I'm glad you think it is a cool puzzle. Yours is an interesting and
innovative solution, but I doubt if the High-Speed Manouvre #1 is safe
enough to be allowed in practice. While you are working on a better
solution, here is a variation to the puzzle:
What if the bridge is too narrow for the coaches but wide enough for
the engine?
Cheers,
Michael.
Dean Edmonds
In article <4u4dh1$g...@sjsun1.cc.ic.ac.uk>,
Michael Chew <m.c...@ic.ac.uk> wrote:
>
>What if the bridge is too narrow for the coaches but wide enough for
>the engine?
Well, let's see if I can get this one in before a dozen others... :)
Move the engine to station A, grab car A and stick it on the depot siding.
Go back through station A, across the bridge to station B and push car B
just past the siding junction. Back up and go down the siding to get A. Back
up off the siding, then connect A to B. Push the AB combo onto the siding,
decouple B, pull A back to station B, decouple A. Back over the
bridge and around to the siding. Grab B, back out of the siding, then push
it into station A. Now go back to the depot.
=============================================================================
- deane | Heard in O'Neill's, home of the PugBurger:
| "You folks are as busy as a horse's tail during fly season!"