Abstract: The invention provides a device for teaching concepts of numbers and mathematical principles comprising a base component having a surface divided into a hundred identical unit squares in ten by ten format, and two series of number elements for use with the base component. Each number element of the first series is dimensioned so that it corresponds exactly in size and shape with a whole number of the unit squares on the base component and displays unit squares corresponding to those unit squares it covers on the base component when it is placed on the base component. Each number element of the first series is marked with the number which it represents in terms of the unit squares. Each number element of the second series has a length corresponding to ten unit squares and a width corresponding to a plurality of unit squares.