Hexagonal Array Puzzle

thingiverse

Here's a puzzle based on an array of ten hexagons whose vertices are numbered: it's a modified version of an illustration used in an article by Choe, Choi, and Moon. Check out the reference at https://en.wikipedia.org/wiki/Hexagonal_tortoise_problem and think about thing:2586578 and thing:2591827. The sums of the numbers at the vertices of nine of the hexagons are 99; a mistake has been made, and the sum of the vertices at the tenth 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 nine hexagons. The answer, the original illustration, is provided, along with paper versions as pdf files. The openSCAD code generates additional arrays that might be useful for study or decoration.