| 摘要 |
The present invention is directed to a system for demonstrating mathematic concepts, such as fractions and their equivalents. The system includes at least one device constituted by a pie chart sheet having a slot, and a rotating disk having a slit. The slit in the rotating disk provides a leading edge which is inserted through the slit on the chart page to allow the rotating disk to cover any selected portion of the chart. Because the cuts in both the pie chart on the chart sheet are radial, rotation of the disk about a common center point is facilitated.
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