Using your Head is Permitted

August 2010 riddle

I have a solid regular tetrahedron whose side is of length 1. I want to pass this tetrahedron through a circular hole in a flat wall of zero thickness.

What is the minimum radius of the hole in order for this to be possible?

You are not required to send a proof this month with your answer (though an explanation of how you got the result would be nice). However, the answer is required to be exact.

List of solvers:

Chen Wei (1 August 22:18)
Albert Stadler (2 August 22:53)
Dan Dima (3 August 07:10)
Itsik Horovitz (7 August 23:22)
Christian Blatter (7 August 23:29)
Joseph DeVincentis (10 August 01:11)
Djinn Lu (10 August 12:15)
John T. Robinson (12 August 01:50)
Daniel Bitin (19 August 02:50)
Adam Daire (21 August 08:00)

Elegant and original solutions can be submitted to the puzzlemaster at Names of solvers will be posted on this page. Notify if you don't want your name to be mentioned.

The solution will be published at the end of the month.


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