1. Subtraction on the Cranmer Abacus – Rule of 5
Sara Larkin
Math Consultant
Iowa Educational Services for the Blind and Visually Impaired
Resource Used: Millaway, S. M. (2002). Abacus basic competency: A counting method. American Printing House for the Blind.

2. Rule of 5
Applies whenever you are moving one bead at a time away from the counting bar, and the rod you are counting on has no more one beads pushed against the counting bar, but does have a five bead set.
Move the five bead away from the counting bar
Return all 4 one beads towards the counting bar

3. Practice Problems
8 – 6
17 – 4
38 – 16
49 – 28