Working on the making 7 congruent triangles from the pieces of a triangle dissection question I realized it's possible to do even better! So here it is for extra points:

Use six lines to cut a triangle into nine congruent triangles.

  • $\begingroup$ I assume that, like the other question, we cannot assume anything about the triangle's shape (it is arbitrary)? $\endgroup$
    – bobble
    Commented Aug 30, 2020 at 20:10
  • $\begingroup$ this one is easier than others $\endgroup$ Commented Aug 30, 2020 at 20:21
  • $\begingroup$ @bobble Yes, arbitrary triangle $\endgroup$
    – Kikos
    Commented Aug 30, 2020 at 21:13
  • 3
    $\begingroup$ square numbers are easy. $\endgroup$
    – Jasen
    Commented Aug 30, 2020 at 22:14
  • 1
    $\begingroup$ Actually, larger number is not always "better" than the smaller number. In this case, the 9 version is apparently (way) more trivial than the 7 version. $\endgroup$
    – athin
    Commented Aug 31, 2020 at 1:17

1 Answer 1



Saves some formatting tokens to not use a spoiler. It's just an image after all.


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