Abstract: An apparatus for teaching mathematics which applies and puts to work in various ways the modern teaching of mathematics for all levels of elementary education through set theory, comprises a horizontal board divided into eleven zones and having two outwardly-projecting subsidiary boards. In use, objects can be placed in selected zones of the horizontal board to demonstrate mathematical operations, and information relating to the operation is written on appropriate zones of the vertical board and on the subsidiary boards. The horizontal board has a bevelled front edge portion on which further information can be written, and two portions in which objects to be placed in the zones of the horizontal board can be placed beforehand.