| 摘要 |
<p>The invention concerns an improved abacus of the type consisting of a stable frame and a series of rods passing through various combinations of spheres and dodecahedra and is characterized in that the abacus is formed by a support frame (1) consisting of two trapezia of a height much greater than the base, disposed opposite one another and connected by at least five rods (2), each rod having a different arrangement of spheres (8) and dodecahedra (9).</p> |
