Bongard Problem #107 (solution)

Left: Exactly three plain (simple) sides.

Right: Exactly three non-plain (complex) sides.

Back to problem #107

Note: Over the years, many people have contacted me and told me what they think the solution to this problem is. Only a very small minority (around 5%) of those who solved this problem managed to see that the number of complex sides on the right side is exactly three. People usually stop upon seeing three plain (simple, straight) sides on the left, and conclude "not three plain sides on the right". Most of the aesthetically pleasing Bongard problems, though, contain a pattern on the right side as well, which is not simply the negation of the left, but a sort of "dual" solution whenever this makes sense and is possible. If you decide to design Bongard problems, remember this, please.