How Do You Connect 9 Dots with 4 Lines?

  • Context: High School 
  • Thread starter Thread starter Rahmuss
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Discussion Overview

The discussion revolves around the classic puzzle of connecting 9 dots with 4 straight lines without lifting the pencil or mouse. Participants share their experiences with the puzzle, explore different interpretations, and discuss potential solutions and variations.

Discussion Character

  • Exploratory
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants recall learning the puzzle in school, emphasizing its nature as a "thinking outside the box" exercise.
  • Several participants express amusement at the frequency with which they encountered the puzzle recently.
  • One participant suggests that it is possible to connect the dots with three lines under certain conditions, such as using a thick pen or manipulating the paper.
  • Another participant argues that connecting all dots with three lines is not feasible unless unconventional methods are applied, detailing how the lines can connect a maximum of 7 dots with three lines.
  • A later reply challenges the assumption that the dots are points, suggesting they are circular and can be connected differently.
  • Some participants inquire about alternative puzzles or similar challenges, indicating a broader interest in such problems.

Areas of Agreement / Disagreement

Participants generally agree on the challenge of the puzzle and its educational value, but there is disagreement regarding the feasibility of connecting the dots with three lines, with multiple competing views on the methods and interpretations involved.

Contextual Notes

Participants express varying assumptions about the nature of the dots and the definition of "straight" lines, which may influence their proposed solutions. Some mention the potential for manipulating the paper or using unconventional tools.

Who May Find This Useful

Individuals interested in puzzles, problem-solving, or educational techniques related to critical thinking may find this discussion engaging.

Rahmuss
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I remember it from grade school too. A real example of thinking outside the box.
 
Funny, we were doing this very problem in school today :-p
 
Very funny, I was talking about this one with friends at Uni today!

As jimmy said, it's definitely one to think outside the box on.
 
I did this in psychology class last year, outside the box is right.
 
This one is pretty cool.
 
Yea, i also learned this from the grad, i think you people and people in my country was quite different, but then this is the same thing we done then...
 
is there is any out side the box puzzle, it is really interesting
 
LOL... that's so funny that so many people were recently doing this one, or had learned it the same way I did. That's great. Well it's a classic then. :biggrin:

Anyone who has not learned it previously have an answer for it?
 
  • #10
Hmm, how abt this?

-- AI
 

Attachments

  • 9dots4bl.gif
    9dots4bl.gif
    1.5 KB · Views: 917
  • #11
That's the one. :smile:
 
  • #12
I'm still puzzling over it, and the forum still refuses to let me view attachments in the brain teasers board. Can anyone describe the answer to me or post an off-site link?

Edit- never mind, googled it.
 
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  • #13
click on the link and then click on log off. Then the image will appear.
 
  • #14
wow, that's a real nice bug
 
  • #15
Wow, I think that's one of the few brainteasers I've gotten within seconds of looking at it... but it wasn't really thinking outside of the box, there were still four 2D lines...
 
  • #16
I wonder if the hints helped. :smile:
 
  • #17
Well, you can do fun things like folding/bending the paper to get even fewer lines.
 
  • #18
The dots aren't points (infinitely small) so you can do it in three if you make the line segments very very long.
 
  • #19
Oh man, for some reason i thought you can't cross the line that you already drew. Otherwise i would have solved it.
 
  • #20
i can't get it
 
  • #21
Nvm i got it. Finally.
 
  • #22
To view attachments you just need to click on it, then when you get the "You need blah blah blah" press logout.

Incase you don't feel like loging out then inn agian I upped TenaliRamans photo to imageshack(I hope that was okay, TenaliRamans ;).
http://img272.imageshack.us/img272/4090/9dots4bl0er.gif
 
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  • #23
I think this puzzle has already been solved.
Can anyone do it with three straight lines without lifting the pen or pencil?
 
  • #24
dipinsingh said:
I think this puzzle has already been solved.
Can anyone do it with three straight lines without lifting the pen or pencil?

I think it should be pretty clear that it's not possible with 3, unless something like:

- you have a REALLY thick pen
- you can manipulate the paper (bend, fold, tear, etc)
- you assume "straight" lines can be something else like "y=2" in polar coordinates
- etc.

Some playing around will demonstrate that you cannot connect more than 3 dots with a single straight line in this example. Hence, your first line can connect 3 dots, and each subsequent line can add as many as 2 additional dots to your connection. So 3 lines will allow you to connect 3+2+2=7 dots, and 4 lines will allow you to connect 3+2+2+2=9 dots.

DaveE
 
  • #25
davee123 said:
I think it should be pretty clear that it's not possible with 3, unless something like:

- you have a REALLY thick pen
- you can manipulate the paper (bend, fold, tear, etc)
- you assume "straight" lines can be something else like "y=2" in polar coordinates
- etc.

Some playing around will demonstrate that you cannot connect more than 3 dots with a single straight line in this example. Hence, your first line can connect 3 dots, and each subsequent line can add as many as 2 additional dots to your connection. So 3 lines will allow you to connect 3+2+2=7 dots, and 4 lines will allow you to connect 3+2+2+2=9 dots.

DaveE


Please note that these are not points but circular dots which can be joined by three straight lines even without thick pen.
Just start from top of first dot, cross from middle of second dot and touch bottom of third dot and extend up to some point such that when u can draw a straight line back joining top of last dot in middle line, centre of middle dot of middle line and then bottom of first dot of middle line.
Similarly draw third line for bottom line dots.
 
  • #26
Last edited by a moderator:
  • #27
http://img213.imageshack.us/img213/1821/3linessmallwc9.png
 
Last edited by a moderator:

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