ABACUS - GENERAL CONCEPTS
a) Abacus
Abacus is a device used by visually impaired children for doing basic mathematical
calculations. Abacus is rectangular in shape. Abacuses with varied columns are used
in different countries. This instructional material is written specifically for the abacus
with 15 columns. The common operations for this abacus are same with those of the
abacuses with fewer columns, but the number of columns matters especially when
fraction problems are solved.
A bar is separating the abacus horizontally cutting across all the fifteen columns,
leaving 32 rd of the area below and 31 rd of the area above.The lower portion is known as lower abacus and the upper portion is known as upper
abacus.Each column in the lower abacus has four beads, each bead assumes the value 1
(one). Each column in the upper abacus has one bead and assumes the value 5 (five).In operation, the extreme right column is treated as the units column, the immediate
left to the units column is the tens column and so on.b) Setting
The process of moving a bead of the lower abacus or the upper abacus towards the
separation bar is called ‘setting’.