| 摘要 |
Educational tools are provided that can include a plurality of sets of placards wherein individual ones of these sets can include a plurality of individual placards, and individual placards within the sets having substantially the same surface area and can be associated with a common symbol. The educational tool can also include at least two of the sets including placards having different surface areas associated with different symbols. Educational methods are also provided that include providing a first set of placards, with the first set of placards including individual placards having a first surface area associated with a first symbol, and providing a second set of placards, with the second set of placards including individual placards having a second surface area associated with a second symbol.
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