Abstract: An educational and entertaining device comprising a set of geometrically identical or proportional elements, each of which includes a plurality of coded indicia bearing surface portions with at least one numeral on each surface portion, the number of elements in said set and the number of said surface portions being identical and at least four in number, said numerals being so related to said coding indicia that if the elements are arrayed such that a differently coded surface portion of each of the elements is disposed for viewing, regardless of which coded surface portion of which element is so disposed, the sum of the numerals on the so disposed surface portions is a constant.