Final Cover - For Printing

c) Clearing
The process of moving a bead away from the separation bar either towards the top of
the upper abacus or the bottom of the lower abacus is called ‘clearing’.

d) Example for complement of a number with respect to the given number
For example, take the number 6. The complement of this number with respect to
number 10 is 4. Hence complement is the value which ‘Completes’ (that is, the
‘remaining’ value with respect to the number which completes).

The complement of the number 6 with respect to the number 100 is 94; the complement

of number 6 with respect to 1000 is 994 and so on.

EXERCISE

What are the complements of:-

i) 7 with respect to 1000

ii) 8 with respect to 10

iii) 15 with respect to 100

e) Dots in the Separation Bar
The dots in the separation bar are helpful for locating the place values of numbers in
abacus.

These dots determine the locations such as whole number, numerator, etc., when fractions

are presented in the abacus. These dots may not be present in some abacuses which

have 13 columns. In such cases, imaginary dots have to be assumed for placing the

numerator, denominator and whole number in the abacus. This does not envisage any

change in the procedures in operation.

After learning the modules on abacus, the learner is expected to demonstrate the
following skills :

1. Ability to formulate problems for addition of one digit, two digits and multiple digits
   and adding them in abacus.