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## #1 2006-05-24 09:35:40

bryan
Member
Registered: 2006-05-24
Posts: 4

### tough one

you have to get heat water and eletric to each house but no lines can cross

heat                      water                    eletric

house 1                        house2                          house3

you can use a infinte amount of paper

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## #2 2006-05-25 04:11:42

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

### Re: tough one

Heehee, I do decision maths so I can prove that that's impossible. =P

Why did the vector cross the road?
It wanted to be normal.

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## #3 2007-03-12 14:56:49

JaneFairfax
Member
Registered: 2007-02-23
Posts: 6,868

### Re: tough one

Okay, Ive been looking at some of these very old threads here

And Ive seen this puzzle before. Here is the solution:
http://puzzles.nigelcoldwell.co.uk/twentysix.htm

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## #4 2007-03-12 16:49:37

Ricky
Moderator
Registered: 2005-12-04
Posts: 3,791

### Re: tough one

I think that is a cheap way out.  Represent each house as a vertex.  Now try it.

"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

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## #5 2007-03-12 16:57:02

JaneFairfax
Member
Registered: 2007-02-23
Posts: 6,868

### Re: tough one

Then Eulers formula comes into play.

http://en.wikipedia.org/wiki/Planar_gra … 7s_formula

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