2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/112971We prove without appeal to the Axiom of Choice that for any sets A and B, if there is a one-to-one correspondence between 3 cross A and 3 cross B then there is a one-to-one correspondence between A and B. The first such proof, due to Lindenbaum, was announced by Lindenbaum and Tarski in 1926, and subsequently `lost'; Tarski published an alternative proof in 1949. We argue that the proof presented here follows Lindenbaum's original.Version dated 1994LogicCombinatorics03E10 (Primary); 03E25 (Secondary)text