Basic Subtraction on the Cranmer Abacus Sara Larkin Math Consultant Iowa Educational Services for the Blind and Visually Impaired

Prerequisites The student should be able to count by rote The student should be able to demonstrate the ability to count the number of objects in a group The student should be able to demonstrate the concept of subtraction by taking a number of objects away from a group and telling you how many are left

Abacus Skills The student must be able to set numbers on the abacus The student must be able to read numbers on the abacus The student must have a knowledge of the terms associated with subtraction on the abacus

Terms for Subtraction Set: To “write” the first number of a subtraction problem on the abacus Count: To move abacus beads, one at a time, away from the counting bar while counting numerically each time a bead is moved. Return: To move either the four beads below the counting bar or the nine beads against the counting bar simultaneously toward the counting bar when a subtraction rule is applied.

Some Basic Problems 9 – 3 14 – 2 35 – – 23

Resource Millaway, S. M. (2002). Abacus basic competency: A counting method. American Printing House for the Blind.