Special Rule, Illustrated by Diagram, for Using Large Divisors on the Comptometer.
COPYRIGHTED 1894, BY FELT & TARRANT MFG. CO.
The regular rule, illustrated on pages 13-17, for computing division, applies to all examples, large or small, but where the divisor exceeds three or four places the following modification of the regular method is more convenient, because, by this modification, the fingers do not have to handle more than two keys at a time. It is also more simple for, by it, only keys in rows are used (except for the two left hand or trial figures of the divisor) the same as in multiplication.
It is useless for one to attempt to divide by this process until the regular process on pages 13-17 is thoroughly understood.
Rule:—Find a quotient figure by using the two left hand figures of the divisor, and then, on the row of keys on which the "large key figure" is the same as the quotient figure, strike for each of the remaining figures of the divisor; thus, suppose a remaining quotient figure to be 6, count "six, seven, eight," striking each time, which, of course, is three times altogether. Or, suppose the remaining quotient figure is 4, count "four, five, six, seven, eight." Always start counting with the figure and stop at eight, except for the extreme right hand figure which must be struck once extra.
NOTES.—If either of the two left hand figures of the divisor be 9, use the first three figures as a trial divisor, because that column in which 9 stands does not have to be struck at all.
If any of the "remaining" figures of the divisor be 9, of course no counts of strokes are made for it unless it is the units figure (last figure) of the divisor when one stroke is given.
If there be a naught (0) among the remaining figures of the divisor count "naught, one, two, three," etc., just the same as for any figure.
In obtaining a quotient figure with the trial divisor it sometimes occurs that the remainder resulting from dividing by the trial divisor nearly equals the trial divisor, and that, striking for the "remaining" figures of the divisor, increases the remainder, until it becomes as great or greater than the trial divisor. In such cases, strike the entire divisor on the keys according to the red figures; this will increase the quotient figure and reduce the remainder.
