Mini Tutorial - how to use the abacus
Referring to the Figure to left, the third column (from the left), representing the number 8 is counted with 1 bead from the top-deck (value 5) and 3 beads from the bottom-deck (each with a value of 1, totaling 3); the sum of the column (5+3) is 8.
Similarly, the fourth column representing the number 7, is counted with 1 bead from the top-deck (value 5) and 2 beads from the bottom-deck (each with a value of 1, totaling 2); the sum of the column (5+2) is 7.
Use the interactive Applet at the top to duplicate the illustration. Notice the value at the top of the frame reflects the repositioning of the beads. See bead value and counting below.
Bead value: Each bead in the upper deck has a value of 5; each bead in the lower deck has a value of 1. Beads are considered counted, when moved towards the beam that separates the two decks.
Counting: After 5 beads are counted in the lower deck, the result is "carried" to the upper deck; after both beads in the upper deck are counted, the result (10) is then carried to the left-most adjacent column.
The right-most column is the ones column; the next adjacent to the left is the tens column; the next adjacent to the left is the hundreds column, and so on. Floating point calculations are performed by designating a space between 2 columns as the decimal-point and all the rows to the right of that space represent fractional portions while all the rows to the left represent whole number digits.
The Abacus Luis Fernandes elf@ee.ryerson.ca
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