Base Five, Abacus, Soroban, そろばん, Suan Pan, 算盘

Base Five is a worthwhile number system to play with: to understand how positional number systems work and to explore alternative number representations (called numerals in a strict sense). In computer science, bases 2, 8, 16 are definitely required. In K-12 education, base five has pedagogical values. One could make an addition or multiplication table just to see how things work.

As expected, in a base five system, we need five symbols: 0, 1, 2, 3, 4. The base five abacus can be used for