abacus

Everyday

1. An abacus is a frame with rows of beads that slide along wires or rods, used for counting and doing sums. tree →
2. In buildings, an abacus is the flat slab on top of a column (architecture word). tree →

In the lessons

In maths lessons, the abacus helps children see place value: each row is a place (ones, tens, hundreds), and moving beads shows adding, taking away and carrying. In history, abacuses were used in ancient Mesopotamia, Greece, Rome and China; the Chinese suanpan and Japanese soroban are still used. Phrases: «count on an abacus», «move the beads».

Examples

• We used an abacus to add 27 and 15. tree →
• On the abacus, the top row shows hundreds and the bottom row shows ones. tree →
• Some children in Japan learn very fast mental maths with a soroban abacus. tree →
• The abacus was used long before calculators. tree →
• Move three beads to the left to add three. tree →
• My little brother counts the coloured beads on his toy abacus. tree →

Note

Plural: abacuses (most common) or abaci (formal). Say «AB-a-kus», stress on the first syllable. Maths: on a place-value abacus, each bead on the tens rod is worth 10, so 3 beads on tens and 4 on ones = 34; ten beads on one row are swapped for one bead on the next row up (carrying).

In Jewish tradition

In maths lessons, the abacus helps children see place value: each row is a place (ones, tens, hundreds), and moving beads shows adding, taking away and carrying. In history, abacuses were used in ancient Mesopotamia, Greece, Rome and China; the Chinese suanpan and Japanese soroban are still used. Phrases: «count on an abacus», «move the beads».

Examples

• ')) Some Pythagoreans used the strokes with the principle of |iosi- tion without a zero in the columns of an abacus i Ur. (Mordell, The Origin of Letters and Numerals according to Sefer Yetzirah (1914)) tree →
• In my opinion, the sexagesimal position originated from the decimal position, and not the reverse ; for the earliest abacus, which was doubtless based on a decimal position, is older than the (Mordell, The Origin of Letters and Numerals according to Sefer Yetzirah (1914)) tree →

Note

Plural: abacuses (most common) or abaci (formal). Say «AB-a-kus», stress on the first syllable. Maths: on a place-value abacus, each bead on the tens rod is worth 10, so 3 beads on tens and 4 on ones = 34; ten beads on one row are swapped for one bead on the next row up (carrying).