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Incubator Q&A Closed loop on a tetrahedron

This puzzle was exactly the right level of difficulty for me. Solution! Click/tap here to reveal In solving this puzzle, I treated the middle triangle as the bottom face of the tetrahedron. Th...

posted 2d ago by will.octagon.gibson‭

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will.octagon.gibson‭ · 2026-09-15T00:13:05Z (2 days ago)

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This puzzle was exactly the right level of difficulty for me.

<details>

<summary>Solution! Click/tap here to reveal</summary>

In solving this puzzle, I treated the middle triangle as the bottom face of the tetrahedron.  The arc on this bottom face could appear in any of three positions.  To reduce the number of possibilities I rotated the tetrahedron so the arc would appear as in the diagram (an upside down U shape).

Then I determined where the edges of the faces would intersect if the faces of the tetrahedron net was folded up to form a tetrahedron.

With a small amount of trial and error I arrived at the following solution:

![Tetrahedron net with an arc on each of the 4 faces.  These 4 arcs form a closed loop.](https://proposals.codidact.com/uploads/4cplnkj4e7q44eabemur8646u4yh)

</details>

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