World Logic Day is a UNESCO-approved date in the academic calendar dedicated to promoting the study of deductive reasoning. It falls next week, and to mark the occasion, a puzzle has been released to get enthusiasts in the mood.
The challenge, known as the Cookie Conundrum, involves three friends: Andy, Bea, and Celine, who share a jar containing ten cookies. They take turns to remove cookies, with Andy going first, followed by Bea, then Celine. On each turn, they may take as many cookies as they wish.
However, there are two conditions. First, no one wants to end up with the most or the least number of cookies; finishing with a joint most or joint least is considered just as undesirable as being the outright winner or loser. Second, each friend wants as many cookies as possible, but the first condition takes priority over the second if they conflict.
The friends are not allowed to communicate or form alliances, and they are not required to take all the cookies—one or more could take nothing. Assuming everyone acts rationally in their own best interests, the puzzle asks how many cookies each friend ends up with.
The puzzle is courtesy of Deniz Sarikaya of World Logic Day, which hosts a list of events. Readers are asked not to reveal the solution, but instead to discuss their favourite illogical arguments.
