Mathematics instructing device

Claim 1

IN A MATHEMATICS INSTRUCTING DEVICE, A STIFF CHART SUPPORTING PANEL, A FRAME FOR SAID CHART SUPPORTING PANEL TO WHICH SAID CHART SUPPORTING PANEL IS JOINED, A CHART POSITIONED UPON A FIRST SURFACE OF SAID CHART SUPPORTING PANEL, SAID CHART BEARING NUMERALS ARRANGED IN A PREDETERMINED ARRAY THEREON, A FIRST STIFF FACTORING MASK HAVING A PLURALITY OF APERTURES THEREIN, EACH APERTURE BEING OF SUFFICIENT SIZE TO EXPOSE ONLY ONE OF SAID NUMERALS ON SAID CHART, WHEREIN SAID PLURALITY OF APERTURES EXPOSE A FIRST GIVEN NUMERAL LESS THAN TEN AND GREATER THAN ONE AS WELL AS MULTIPLES THEREOF, WHEN SAID FIRST MASK IS POSITIONED IN REGISTRATION WITH SAID CHART, AND AT LEAST A SECOND STIFF FACTORING MASK HAVING A PLURALITY OF APERTURES THEREIN, EACH APERTURE BEING OF SUFFICIENT SIZE TO EXPOSE ONLY ONE OF SAID NUMBERLS ON SAID CHART, WHEREIN SAID PLURALITY OF APERTURES IN SAID SECOND MASK EXPOSE A SECOND GIVEN NUMERAL DIFFERENT FROM FIRST GIVEN NUMERAL, AND MULTIPLES THEREOF, WHEN SAID SECOND MASK IS POSITIONED IN REGISTRY WITH THE CHART, SUCH SECOND GIVEN NUMERAL ALSO BEING LESS THAN TEN AND GREATER THAN ONE, SAID FRAME HAVING PORTIONS EXTENDING FORWARD OF THE FIRST SURFACE OF SAID CHART SUPPORTING PANEL UPON WHICH SAID CHART IS POSITIONED TO FORM A COMPARTMENT OF A DEPTH EQUAL TO AT LEAST THE COMBINED THICKNESS OF SAID FIRST FACTORING MASK AND SAID SECOND FACTORING MASK IN REGISTRY, BOTH SAID FACTORING MASKS BEING SLIDABLY RECEIVABLE IN GUIDED RELATION INTO SAID COMPARTMENT, A PORTION OF SAID FRAME FORMING A BACKSTOP FOR REGISTERING SAID MASKS WITH SAID CHART, SAID APERTURES CONJOINTLY EXPOSING NUMERALS OF WHICH BOTH SAID FIRST GIVEN NUMERAL AND SECOND GIVEN NUMERAL ARE FACTORS.