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Brevetto:US 3147556
Titolo:Calculating Device
Nazione:Stati Uniti
Persona:Prusmack, Murray (P)
Link interni:Rechenschieber, ABA-Ten Rule, Lehrmittel
Keywords:slide rule
Link al brevetto:
(without guarantee)
 US3147556 ( (espacenet),  US3147556 ( (uspto)

"This invention relates to teaching aids and more particularly to a new and useful calculating device for introducing children of the kindergarten and lower grammar school grades to basic concepts in various branches of mathematics.

It is a primary object of present coordinates the sense of touch with the sense of sight to physically present and demonstrate a variety of basic number groupings in the arts of addition, subtraction, multiplication, and division and the number facts of these groupings in a manner which assists the young student in correlating abstract numerical symbols with corresponding physical entities." Aus der Patentschrift.

aus der Patentschrift

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Ultima modifica il 16:59, 18. Ott 2007.