Tying unit cubes to a thread and building a cuboid
Source: Bundeswettbewerb Mathematik 2024, Round 1 - Problem 4
March 8, 2024
combinatoricscombinatorics proposed
Problem Statement
For positive integers , and we are given unit cubes. We drill a hole along the space diagonal of each of these cubes and then tie them to a very thin thread of length like a string of pearls.We now want to construct a cuboid of side lengths , and out of the cubes, without tearing the thread.
a) For which numbers , and is this possible?
b) For which numbers , and is this possible in a way such that both ends of the thread coincide?