一、文章
PASSAGE · 点击任意单词可查词典
P1
It seems very natural that if you have two dollars and add two dollars to them. You have four dollars. But do you know it took men millions of years to be able to think this way? In fact, one of the most difficult things to teach children is the idea of numbers.
P2
In ancient times when a man wanted to tell how many animals he owned, he had no system of numbers to use. He put a stone into a bag for each animal. The more animals, the more stones be had. It may explain why the word “calculate” comes from the Latin word “calculus”. “Calculus” means “stone”.
P3
Then, the man used lines to count. People would just draw a line for each thing they wanted to count, but they had no word to tell the number.
P4
Later on, people used fingers. Again, we have the word that goes back to this. The word “digit” comes from the Latin word “digitus”. It means “finger”! And the fact that we have 10 fingers led to the use of 10 in the system of numbers.
P5
The number system we use today was invented by the Hindus in India thousands of years ago and was brought to Europe during the 8th to 11th century by Arab traders (商人). In this system, people count things with ten numbers: 1.2.3.4.5.6.7.8.9. and 0. It is decimal system, that is, it is built on the base of 10.
原卷印刷说明：① P2 中 “the more stones be had” 是原卷排版错误，规范写法应为 “the more stones he had”；② 第 17 题 C 项原卷印作 “Bight”，是 “Eight” 的印刷错误，本页已按 Eight 呈现。
三、文章精读
INTENSIVE READING · 词性套色 + 从句划线
精读说明：按《词性标注配色规则》套色——绿=谓语动词，绿底=不定式，墨绿+灰底=动名词，玫红=形容词/形容词性物主代词，玫红+粉底=分词，蓝=副词，紫=介词，橙=连词，橙底=that 类引导词，蓝底=wh- 类引导词，红=疑问词，深灰=冠词/代词/名词；句子下的橙色下划线=that 类从句，蓝色下划线=wh- 类从句。点击生词可查词典。
配色速查
谓语动词
不定式
动名词
形容词/物主代词
分词
副词
介词
连词
that 类引导词
wh- 类引导词
疑问词
冠词/代词/名词
P1 · 数字的概念
S1It seems very natural that if you have two dollars and add two dollars to them.如果你有两美元，再加上两美元，这看起来非常自然。
S2You have four dollars.你就有四美元。
S3But do you know it took men millions of years to be able to think this way?但你知道人类花了几百万年才能够这样思考吗？
S4In fact, one of the most difficult things to teach children is the idea of numbers.事实上，最难教给孩子的事情之一就是数字的概念。
P2 · 用石头计数
S1In ancient times when a man wanted to tell how many animals he owned, he had no system of numbers to use.在古代，当一个人想说出自己拥有多少动物时，他没有可用的数字系统。
S2He put a stone into a bag for each animal.他为每只动物往袋子里放一块石头。
S3The more animals, the more stones he had.动物越多，他的石头就越多。（原卷此处印作 “be had”，应为 “he had”。）
S4It may explain why the word “calculate” comes from the Latin word “calculus”.这也许能解释为什么 “calculate” 这个词来自拉丁语 “calculus”。
S5“Calculus” means “stone”.“Calculus” 的意思是“石头”。
P3 · 用线条计数
S1Then, the man used lines to count.后来，人类用线条来计数。
S2People would just draw a line for each thing they wanted to count, but they had no word to tell the number.人们只是为他们想数的每样东西画一条线，但他们没有词来表达这个数字。
P4 · 用手指计数
S1Later on, people used fingers.再后来，人们用手指计数。
S2Again, we have the word that goes back to this.同样，我们有一个词可以追溯到这一点。
S3The word “digit” comes from the Latin word “digitus”.“digit” 这个词来自拉丁语 “digitus”。
S4It means “finger”!它的意思是“手指”！
S5And the fact that we have 10 fingers led to the use of 10 in the system of numbers.而我们有 10 根手指这一事实，导致了计数系统中使用 10。
P5 · 十进制的诞生
S1The number system we use today was invented by the Hindus in India thousands of years ago and was brought to Europe during the 8th to 11th century by Arab traders .我们今天使用的数字系统是几千年前由印度的印度人发明的，并在 8 至 11 世纪由阿拉伯商人带到欧洲。
S2In this system, people count things with ten numbers: 1.2.3.4.5.6.7.8.9. and 0.在这个系统中，人们用十个数字来计数：1 到 9 以及 0。
S3It is decimal system, that is, it is built on the base of 10.它就是十进制系统，也就是说，它以 10 为基数。
四、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 1
It took men millions of years to be able to think this way.
It took men / us / the scientists millions of years / a long time / ten years to be able to think this way / finish the work / make the invention.
仿写：It took the scientists ten years to make the invention. 科学家们花了十年时间才做出这项发明。
适用：表达“花费时间做某事”（It takes sb. + 时间 + to do sth.）。
金句 2
People would just draw a line for each thing they wanted to count.
People drew a line / made a mark / took a photo for each thing / animal / place they wanted to count / record / remember.
仿写：People took a photo for each place they wanted to remember. 人们为每个想记住的地方拍一张照片。
适用：说明过去反复发生的做法（would + 动词原形）。
金句 3
The fact that we have 10 fingers led to the use of 10 in the system of numbers.
The fact that we have 10 fingers / he works hard / she practises every day led to the use of 10 in the system of numbers / his success / her progress.
仿写：The fact that she practises every day led to her progress. 她每天练习这一事实带来了她的进步。
适用：表达“某事导致某结果”（The fact that ... led to ...，含同位语从句）。