The arithmographe “Ki Ser” is a small cylinder on which two mobile barems can be viewed simultaneously.

Cet arithmographe multiplie des chiffres allant de 15 à 95 par des chiffres allant de 100 à 1000.

To multiply 895 by 75, one rotates the sliding scale until 95 appears in the transparent window of 8 and refer to the intersection of column 75 and line 8. There are two numbers to add up: 600 (8×75) and 7,125. The addition of these two numbers taking into account their respective positions gives 67,125.

To facilitate its use by French merchants, figures are expressed in francs and centimes.