Education and demonstration – Mathematics – Arithmetic
Patent
1994-11-21
1997-02-04
Hirsch, Paul J.
Education and demonstration
Mathematics
Arithmetic
434211, G09B 2302
Patent
active
055991882
ABSTRACT:
A didactic-educational toy for elementary arithmetic operations includes a plurality of transparent plates. Each of the transparent plates has ten circular orifices. The orifices are distributed symmetrically in two rows. Each row has five of the orifices. Each of the orifices has substantially the same diameter. A plurality of plates each has cylindrical stepped protuberances. Each of the protuberances has a base with a diameter corresponding to a diameter of the orifices of the transparent plates to provide for close-fitting insertion of the base into a corresponding one of the orifices. Each of the protuberances has an upper portion having a diameter smaller than the diameter of its base to facilitate the insertion of the protuberance into a corresponding orifice. The plurality of plates, which have cylindrical stepped protuberances include plates has a different number of protuberances. The surface area of each plate is substantially proportional to the number of protuberances. The plurality of plates, which have cylindrical stepped protuberances include at least a plurality of plates having only one protuberance and a plurality of plates having two protuberances.
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