It refers to a module composed of four wooden boxes, which are divided into three, four, six and nine lockers on its front face; on its last face, there is a sliding cover, which can move the plastic plates from zero to nine. Each box has a curved metal strip that extends from the bottom to the top of the box. In addition, there are 18 plastic balls or balls on each metal bar. This is to make it easier for students to understand decimal numbers.
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