when was the abacus invented in ancient china
2nd century BC
title: Abacus text: Abacus The abacus ("plural" abaci or abacuses), also called a counting frame, is a calculating tool that was in use in Europe, China and Russia, centuries before the adoption of the written Hindu–Arabic numeral system. The exact origin of the abacus is still unknown. Today, abacuses are often constructed as a bamboo frame with beads sliding on wires, but originally they were beans or stones moved in grooves in sand or on tablets of wood, stone, or metal. Abacuses come in different designs. Some designs, like the bead frame consisting of beads divided into tens, are used mainly to teach title: Abacus text: Vase" was unearthed in 1851. It was covered with pictures including a "treasurer" holding a wax tablet in one hand while manipulating counters on a table with the other. The earliest known written documentation of the Chinese abacus dates to the 2nd century BC. The Chinese abacus, known as the "suanpan" (算盤, lit. "calculating tray"), is typically tall and comes in various widths depending on the operator. It usually has more than seven rods. There are two beads on each rod in the upper deck and five beads each in the bottom. The beads are usually rounded and made of title: Abacus text: scholars concentrated on exchanging knowledge and inventions with the countries around them – India, China, and the Roman Empire, when it is thought to have been exported to other countries. The earliest archaeological evidence for the use of the Greek abacus dates to the 5th century BC. Also Demosthenes (384 BC–322 BC) talked of the need to use pebbles for calculations too difficult for your head. A play by Alexis from the 4th century BC mentions an abacus and pebbles for accounting, and both Diogenes and Polybius mention men that sometimes stood for more and sometimes for less, like the title: Abacus text: a hardwood. The beads are counted by moving them up or down towards the beam; beads moved toward the beam are counted, while those moved away from it are not. The "suanpan" can be reset to the starting position instantly by a quick movement along the horizontal axis to spin all the beads away from the horizontal beam at the center. The prototype of the Chinese abacus is the appeared during the Han Dynasty, and the beads are oval. In the Song Dynasty or before used the 4:1 type or four beads abacus similar to the modern abacus or commony title: Abacus text: which was still common in China. Today's Japanese abacus is a 1:4 type, four-bead abacus was introduced from China in the Muromachi era. It adopts the form of the upper deck one bead and the bottom four beads. The top bead on the upper deck was equal to five and the bottom one is equal to one like the Chinese or Korean abacus , and the decimal number can be expressed, so the abacus is designed as one four abacus. The beads are always in the shape of a diamond. The quotient division is generally used instead of the division