Generally, an abacus has one bead above and four beads below. The lower bead stands for 1 and the upper bead stands for 5. If 1, dial one bead at the bottom, 2, dial another bead. 4 Just dial four beads, and when it is five, dial down the upper bead and the lower four.

Generally, from the ninth gear to the fifteenth gear, the beam is placed horizontally on the gear, two beads are placed on the beam, each bead counts as five, and five beads are placed under the beam, each bead counts as one. Calculate the beads after positioning, and you can do algorithms such as addition, subtraction, multiplication and division.

Abacus formula

Abacus subtraction formula is non-abdication subtraction, abdication subtraction, direct subtraction, five-rest subtraction, abdication subtraction and ten-retreat five-complement subtraction.

The formula of addition is direct addition, full five plus, ten plus, broken fifty percent plus, one to one, five to four, one to nine, one to two, two to five to three, two to eight to three, three to five to two, three to seven to one, four to four, four to five to four to six to one, five to five, five to five to one.