Teaching aid for teaching addition and subtraction

摘要

The present invention provides an improved teaching aid for teaching addition and subtraction of real numbers which may be easily mastered by children or students. The teaching aid includes a slide (20) and a rule (30). The rule is inscribed with a scale (31). The slide is inscribed with a pointer (25) and indicia (21, 22, 23, 24) indicating the appropriate movement of the slide relative to the scale as a function of the sign of the real numbers desired to be added or subtracted. In certain aspects of the invention, the indicia include arrows (23, 24, 43, 44), and positive and negative signs, and combinations thereof. The slide and the rule are so configured and arranged that the pointer (25) and the scale (31) are in relative alignment. In some aspects, the rule is inscribed with one or more real numbers (32, 32a, 32b, 32c).