Activities/Abacus
Where to get Abacus
About Abacus
Abacus lets the learner explore different representations of numbers using different mechanical counting systems developed by the ancient Romans and Chinese. There are several different variants available for exploration: a suanpan, the traditional Chinese abacus with 2 beads on top and 5 beads below; a soroban, the traditional Japanese abacus with 1 bead on top and 4 beads below; the schety, the traditional Russian abacus, with 10 beads per column, with the exception of one column with just 4 beads used for counting in fourths; and the nepohualtzintzin, a Mayan abacus, 3 beads on top and 4 beads below (base 20).
suanpan (Chinese)
soropan (Japanese)
schety (Russian)
nepohualtzintzin (Mayan)
How to use an abacus
Clear the abacus
Before you start an arithmetic operation, you need to "clear" the abacus. The upper beads should be positioned against the top of the frame and the lower beads should be positioned against the bottom of the frame. This is the default position for the abacus when you launch the activity. (Note that the schety does not have any upper beads. All of the beads in the schety should start in the down position.)
Reading the abacus
In each column, the bottom beads represent 1s and the top beads represent 5s. (The exception is the column in the schety with only 4 beads. These are 1/4 each.) So for each bead you raise up from the bottom in a column add 1 and for each bead you lower from the top in the same column, add 5.
The columns themselves represent decimal positions from right to left, e.g., 1s, 10s, 100s, 1000s, etc. (There are two exceptions: (1) the nepohualtzintzin uses base 20, e.g., 1s, 20s, 400s, 8000s, etc.; and (2) on the schety, the beads to the right of the column with just four beads are 0.1s, 0.01s, 0.001s, and 0.0001s.)
The current value is always displayed on the frame. Experiment and you will quickly learn to write and read numbers.
Note: The display always assumes a fixed unit column, but you can override this choice.
TODO: add an indicator for assigning the unit column.