用英语哦,介绍一下算盘的来历和用途

An abacus,also called a counting frame,is a calculating tool used primarily by Asians for performing arithmetic processes.Nowadays,abaci are often constructed as a wooden frame with beads sliding on wires,but originally they were beads or stones moved in grooves in sand or on tablets of wood,stone,or metal.The abacus was in use centuries before the adoption of the written modern numeral system and is still widely used by merchants and clerks in China,Japan,Africa,India and elsewhere.
The user of an abacus is called an abacist; he or she slides the beads of the abacus by hand.

The Chinese abacus known as the suànpán is typically 20 cm tall and it comes in various widths depending on the operator. It usually has more than seven rods. There are two beads on each rod in the up...

呵呵 亲爱的 这不是 第九单元 的 那个 短文 么 自己 不会 写 么 其实 很简单的 是不是 上课 不认真 听捏 呵呵

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。。。。搜篇中文的自己翻译机去