In the second grade, the abacus used in the abacus mental arithmetic teaching aid is all five beads, which is convenient to carry.

The difference between the five-bead abacus and the seven-bead abacus is that the five-bead abacus is up and down, and the seven-bead abacus is up and down. The calculation methods of seven-bead abacus and five-bead abacus are different, which leads to different structures.