Let's say you have a standard bagel (one that is NOT pre-sliced). How can you cut this bagel into two interlocking rings? The rings must never be broken.

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    $\begingroup$ georgehart.com/bagel/bagel.html $\endgroup$
    – skv
    Nov 6, 2014 at 9:01
  • $\begingroup$ @skv That's an answer ;-) $\endgroup$
    – Joe
    Nov 6, 2014 at 9:44
  • $\begingroup$ :) Yes, I just did not feel good about writing that out as an answer because it was not nearly mine, also I could not modify anything there to make it sound like I have added value, so just left it there $\endgroup$
    – skv
    Nov 6, 2014 at 9:49
  • $\begingroup$ The answer @skv posted is the only one that can fulfill the requirements, I think.. $\endgroup$ Nov 6, 2014 at 10:56

1 Answer 1


Ok Just to ensure that this question gets an answer I am posting this, and attributing it to community.

Credits to http://www.dailymail.co.uk/sciencetech/article-2232924/How-make-Mobius-bagel-Sliced-just-right-breakfast-snack-makes-linked-halves-curious-mathematical-properties.html

The basic concept is to consider the third dimension and visualize four key points. Center the bagel at the origin, circling the Z axis.

A is the highest point above the +X axis. B is where the +Y axis enters the bagel. C is the lowest point below the -X axis. D is where the -Y axis exits the bagel.

Cut through the line ABCDA. Then turn the bagel over and make the same cut again. Here is a video showing how to cut the bagel.

enter image description here

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    $\begingroup$ I changed the image because I think it would be useful to show the line you need to cut through, as well as the final result. $\endgroup$ Nov 6, 2014 at 14:48
  • $\begingroup$ Is the red line just the other end of the same cut? That is, 180 degrees opposite the black line? $\endgroup$ Nov 6, 2014 at 15:20
  • $\begingroup$ @EnvisionAndDevelop You have to turn the bagel over and make the same cut again - I edited the answer to reflect that and included a link to a video. $\endgroup$ Nov 6, 2014 at 15:34
  • $\begingroup$ Why\how is there 'slightly more surface area'? $\endgroup$
    – Mazura
    Nov 7, 2014 at 10:31

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