Yoruba subtractive vigesimal numeration
Numeración vigesimal sustractiva yoruba
- Date
- documentada en 1843 (origen antiguo) · confidence low
- Place
- Oyo, Nigeria
- Credited to
- Yoruba people
- Field
- Knowledge & symbols
⚠️ Disputed: the sources disagree.
What it is
A base-20 system that forms many numbers by subtracting from the next score (45 is said as '60 minus 10 minus 5'). It requires mental calculation with additions, subtractions and multiplications for every number.
Recorded in Samuel Ajayi Crowther's Yoruba vocabulary (1843); its antiquity is unknown. Zaslavsky (Africa Counts, 1973) popularised it.
What it led to
- mental arithmetic in Yoruba market trade
- the study of the diversity of numeral systems
- African ethnomathematics