| 摘要 |
A teaching device for teaching mathematics in the primary grades including a board having a plurality of openings extending between opposite sides with a movable plug in each of the openings. Each plug has a cardinal number on opposite ends thereof and is axially movable between first and second positions, the same number being on both ends of a given plug. In a device for teaching addition and subtraction, the numbers on the plugs are preferably arranged to form a number line that extends consecutively from one side of the device to the other. A chart for each of the plugs is provided on one surface of the board, with the chart having a plurality of groups of numerical values each having a mathematical solution equal to the cardinal number of the associated plug, so that a person facing one surface of the board may perform a problem solving function and a person facing the other surface of the board can perform an answer checking function.
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