阅读原文
Passage · 数字的种类、古代计数系统与十进制
P1Numbers are used for counting, and comparing amounts. A number system is a set of symbols to show numbers.
P2Kinds of Numbers — Numbers can be divided in many ways. The simplest ones are integers (整数), such as -1, -2, 0, 1, 2. Among them, numbers that are greater than 0 are called positive integers, and numbers that are less than 0 are called negative integers.
P3Ancient Number Systems — The first system of numbers was probably the tally system. In this system, a mark was made for everything being counted. But this system was useful only when counting small numbers. Later, the ancient Egyptians developed a system for writing large numbers in symbols. The ancient Romans used letters to show numbers — I for 1, V for 5, X for 10, L for 50, C for 100, D for 500, and M for 1,000. In the Roman system, 256 is written as CCLVI.
P4Base-ten and Other Systems — The most common number system used today is called the base-ten. It has 10 figures (0 ~ 9) that can be used to write any number. The base-ten system was invented by Hindus. Later, Arabs improved the system. For this reason, the figures 0 ~ 9 are called Hindu-Arabic numerals. In the base-ten system, the value of each figure is based on its "place" in a number. There is an "ones place", a "tens place", a "hundreds place", and so on. For some purposes, other number systems are more useful than base-ten. For example, computers use the base-two. Instead of 10 figures, this system uses only two — 0 and 1.
文章精读
INTENSIVE READING · 词性标注 + 句型分析
按词性标注颜色读句子：绿色=动词，粉字=形容词，蓝字=副词，紫字=介词，橙字=连词，带底纹=词形变化。点击生词仍可查词典。
P1 · 数字与数字系统
S1Numbers are used for counting, and comparing amounts.数字用于计数和比较数量。
S2A number system is a set of symbols to show numbers.数字系统是一套用来表示数字的符号。
P2 · 数字的分类
S1Kinds of Numbers — Numbers can be divided in many ways.数字的种类——数字可以按很多方式分类。
S2The simplest ones are integers, such as -1, -2, 0, 1, 2.最简单的数字是整数，如 -1、-2、0、1、2。
S3Among them, numbers that are greater than 0 are called positive integers, and numbers that are less than 0 are called negative integers.其中，大于 0 的数叫正整数，小于 0 的数叫负整数。
P3 · 古代数字系统
S1Ancient Number Systems — The first system of numbers was probably the tally system.古代数字系统——最早的计数系统可能是刻痕计数法。
S2In this system, a mark was made for everything being counted.在这个系统中，每数一样东西就做一个记号。
S3But this system was useful only when counting small numbers.但这种方法只在数小数字时有用。
S4Later, the ancient Egyptians developed a system for writing large numbers in symbols.后来，古埃及人发明了一套用符号书写大数字的系统。
S5The ancient Romans used letters to show numbers — I for 1, V for 5, X for 10, L for 50, C for 100, D for 500, and M for 1,000.古罗马人用字母表示数字——I 表示 1，V 表示 5，X 表示 10，L 表示 50，C 表示 100，D 表示 500，M 表示 1000。
S6In the Roman system, 256 is written as CCLVI.在罗马数字系统中，256 写作 CCLVI。
P4 · 十进制与其他进制
S1The most common number system used today is called the base-ten.当今最常用的数字系统叫十进制。
S2It has 10 figures that can be used to write any number.它有 10 个数字（0~9），可以用来写出任何数。
S3The base-ten system was invented by Hindus.十进制系统是由印度人发明的。
S4Later, Arabs improved the system.后来，阿拉伯人改进了这个系统。
S5For this reason, the figures 0 ~ 9 are called Hindu-Arabic numerals.因此，数字 0~9 被称为印度-阿拉伯数字。
S6In the base-ten system, the value of each figure is based on its "place" in a number.在十进制中，每个数字的值取决于它在数中的“位置”。
S7There is an "ones place", a "tens place", a "hundreds place", and so on.有个位、十位、百位，等等。
S8For some purposes, other number systems are more useful than base-ten.出于某些用途，其他数字系统比十进制更有用。
S9For example, computers use the base-two.例如，计算机使用二进制。
S10Instead of 10 figures, this system uses only two — 0 and 1.与十位数字不同，这个系统只用两个数字——0 和 1。
作文金句仿写
WRITING BOOST · 黑色为框架，灰色底纹为可替换词
把文中的好句子拆成“句型框架”，换上你自己的词，就能写出漂亮的句子。
金句 1Numbers are used for counting and comparing amounts.
Numbers / Mobile phones / The Internet are / is used for counting / communicating / learning.
仿写：The Internet is used for learning and communicating. 互联网被用来学习和交流。
适用：介绍某事物的用途。
金句 2The value of each figure is based on its place in a number.
The value / success / decision is / was based on its place / hard work / careful thinking.
仿写：His success is based on hard work. 他的成功基于努力。
适用：表达“某结果建立在……之上”。
金句 3Instead of 10 figures, this system uses only two — 0 and 1.
Instead of 10 figures / watching TV / giving up, this system / I / he uses only two / reads books / keeps trying.
仿写：Instead of giving up, he keeps trying. 他没有放弃，而是不断尝试。
适用：表达“不是……而是……”的对比。
