Here is a puzzle based on an array of ten hexagons whose vertices are numbered. It is a modified version of an array used as an illustration in an article by Choe, Choi, and Moon. See the reference in the wikipedia article: https://en.wikipedia.org/wiki/Hexagonal_tortoise_problem and also thing:2586578 and thing:2591827

The sums of the numbers at the vertices of 9 of the hexagons are 99; an error has been introduced and the sum of the vertices at the 10th hexagon is 98.

1. Find the hexagon with the incorrect sum.

2. Switch numbers at the vertices of the hexagons so as to fix the incorrect sum without changing the sums at the other 9 hexagons.

The answer, (the original illustration), is given. Paper versions as pdf files are also given.

The openSCAD code generates other arrays which might be useful for study or decoration.