| 摘要 |
PROBLEM TO BE SOLVED: To provide an arithmetic abacus for enabling a user to visualize the addition and subtraction of digits and preventing any loss of calculation beads. SOLUTION: This arithmetic abacus is provided with a plurality of supporting rods (20, 21) arranged side by side across an adjacent calculation area A1 and a non-calculation area A2 and 10 pieces of calculation board 30 mounted on each of those supporting rods (20, 21) so as to not to be removable and mounted in the axial line direction of each of those supporting rods (20, 21) so as to be movable either independently or in a batch. Also, 10 pieces of absence display marks 40 are arranged at the lower part of each of those supporting rods (20, 21) so as to be invisible when those 10 pieces of calculation beads 30 are adjacently arranged at fixed positions in the calculation area A1, and so as to be visible when the calculation beads 30 are moved to the non-calculation area A2.
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