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This will be a very straight forward puzzle accessible to anybody with no special skills required.

enter image description here

In this grid of dots, draw 12 straight lines and connect all the dots. The lines must be drawn end to end (imagine making the lines with a pencil and not ever picking up the pencil). The lines' thickness can't help with the puzzle; for all intents and purposes the line thicknesses are infinitesimal. The lines must also go through the center of each point.

Rules:

1) No putting the grid on a non-flat surface

2) Post a picture of your solution (the lines can be thick but the thickness can't help with the solution)

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  • $\begingroup$ Quark, could I use that image? $\endgroup$
    – warspyking
    Commented Jan 11, 2015 at 15:34
  • $\begingroup$ Yeah if you want, I found it on I think a MIT puzzle site or something like that. (and I doubt there's a copyright or anything similar on a bunch of dots) $\endgroup$
    – Quark
    Commented Jan 12, 2015 at 15:22

2 Answers 2

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enter image description here
Just the standard 3x3 solution, but extended with a spiral.

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    $\begingroup$ Well that was fast, I guess if you've seen it it's kinda trivial :p $\endgroup$
    – Quark
    Commented Jan 11, 2015 at 8:20
  • $\begingroup$ Is it know the minimal number of lines for square n-by-n set of dots? $\endgroup$
    – Nick
    Commented May 13, 2020 at 16:18
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12 lines, 7x7

I've found there are many solutions that use the 3x3 trick of going out of bounds.

There may even be one with 11 lines, considering I've got around many overlapping points on several solutions.

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  • $\begingroup$ This gives me an idea for a seperate puzzle... $\endgroup$
    – warspyking
    Commented Jan 11, 2015 at 15:33

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