MIE 2016/Day 1/Problem 10

Problem 10

A hexagon is divided into 6 equilateral triangles. How many ways can we put the numbers from 1 to 6 in each triangle, without repetition, such that the sum of the numbers of three adjacent triangles is always a multiple of 3? Solutions obtained by rotation or reflection are differents, thus the following figures represent two distinct solutions.

(a)

(b)

(c)

(d)

(e)

See Also

The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.