Title: Arithmetic device

Abstract: A plurality of rectangular blocks are juxtaposed in a rectangular coordinate ordered array to define a generally planar exposed surface with the opposite surface of the blocks attached to a flexible backing which functions as a hinge to allow a linear array of blocks to be pivoted parallel to a rectangular coordinate and expose indicia on the juxtaposed surfaces of the linear array, the indicia being related to other indicia on the exposed surface of the array such as the product of multiplying the two numbers along coordinate edges of the array.

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Inventors: Lufkin, James Alan (Piedmont, CA, US)
Peterson, Paul E. (Piedmont, CA, US)

Application Number: 637381
Filing Date: 1975-12-03
Publication_date: 1976-12-28
Assignee:
Primary Class(es): 434/208 434/209
Other Classes:
US Patent Ref:

3487578	Jan, 1970	Sudermann	273/155.
3550310	Dec, 1970	Bock-Greissau	273/155.
3628261	Dec, 1971	Thompson	35/70.
3836418	Sep, 1974	Montgomery	273/155.

Other Refs: 745,872

Feb, 1933	FR

Primary Examiner: Skogquist, Harland S.
Assistant Examiner:
Attorney: Tipton; Robert R.