九年级英语全册《unit 9 when was it invented-fascinating facts about the invention》文章素材 人教新目标版
2页1、Unit 9 When was it invented-Fascinating facts about the invention文章素材Calculation was a need from the early days when it was necessary to account to others for individual or group actions, particularly in relation to maintaining inventories (of flocks of sheep) or reconciling finances. Early man counted by means of matching one set of objects with another set (stones and sheep). The operations of addition and subtraction were simply the operations of adding or subtracting groups of objects to the
2、 sack of counting stones or pebbles. Early counting tables, named abaci, not only formalized this counting method but also introduced the concept of positional notation that we use today. The next logical step was to produce the first personal calculatorthe abacuswhich used the same concepts of one set of objects standing in for objects in another set, but also the concept of a single object standing for a collection of objectspositional notation. The Chinese abacus was developed about 5000 year
3、s ago. It was built out of wood and beads. It could be held and carried around easily. The abacus was so successful that its use spread form China to many other countries. The abacus is still in use in some countries today.The abacus does not actually do the computing, as todays calculators do. It helps people keep track of numbers as they do the computing. People who are good at using an abacus can often do calculations as quickly as a person who is using a calculatorThis one-for-one correspond
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