Abstract: A teaching aid procreated to develop learner participation in mental computation of number combinations involving all of the elements of basic arithmetic. Four elongated slide members are permanently housed within the confines of a frame member. Each slide member has the numerical figure indicia of from one to twelve printed thereon. The frame means has four windows therein. Each window is associated with one of the slide members whereby movement of the slide members will cause various numbers to be viewable therethrough. Arithmetic function indicia is printed on the frame member between the windows whereby various arithmetic problems can be displayed by movement of the slide members to cause selected numerical figure indicia to be viewable through the windows.