Last modified on Mon 11 Jan 2021 12.03 EST Today’s puzzle concerns these three folk standing in a line, as illustrated below. They are all extremely logical people, and they can only see who is in front of them. A hat seller shows them three white and two black hats. She places a hat on each person and hides the remaining two. She asks: “Does anyone know what colour hat they have?” No answer. No answer. One person answers. Which person and what colour hat? Illustration: M Erazo [To be clear: the people in the line can only see the hats of the people in front of them, which they know come from a set of three white and two black hats. Before the seller asks her first question they have no other information.]