| 摘要 |
An aid for teaching children addition and subtraction of two numbers according to an algebraic equation. Cards bearing selected integers and one card bearing a plus or minus sign are placed by the teacher on a panel in horizontally aligned spaces corresponding to the terms of the equation but for one space. The student is then challenged to hang a card displaying the appropriate integer or sign in the vacant space. Rings slidable on a horizontal rod are positionable in the spaces in quantities corresponding to the integers thereat for visual reinforcement of the equation.
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