nit 3 Trip to the Three Gorges - —Division by Decimals 三 游三峡 ——小数除法
Lesson 1 On June 1, 2003, Sanxia Dam was officially filled with water. The water level rose by 9.84 meters in three days. 2003年6月1日，三下大坝正式蓄水。蓄水三天水位上升了9.84米。 Three Gorges Level 5 Lock is 6.4 kilometers long and takes 2.5 hours for cruise ships to pass. 三峡5级船闸全长6.4千米，游船通过需要2.5小时。 What questions can you ask? 你能提出什么问题？ Cooperative exploration 合作探索 1. How many meters does the water level rise on average every day? 1. 水位平均每天上升多少米？ Nine point eighty four divided by three equals to ______(m) 9.84÷3＝________(米) 2. What is the average time to pass through each class of lock? 2. 通过每级船闸的平均时间是多少小时？ Two point five divided by five equals to______(hour) 2.5÷5＝_________(时) 3. How many kilometers is the average length of each lock class? 4. 平均每级船闸长多少千米？ Six point four divided by five equals to ______(㎞) 6.4÷5＝_________(千米) Can you calculate 13÷2? 你会计算13÷2吗？ Think about it. How do you calculate a decimal division when the divisor is an integer? 想一想，怎样计算除数是整数的小数除法？
Lesson 2 The shortest of the 24 locks, which is 38.5 meters high and 20.2 meters wide and nearly the size of two basketball courts, is known as "the best gate in the world." 三峡永久船闸的闸门共有24扇，其中最短的一扇闸门高38.5米、宽20.2米，面积接近两个篮球场大，被称为“天下第一门”。 My door is 2.2 meters high。 我家的门高2.2米。 What questions can you ask? 你能提出什么问题？ Cooperative exploration 合作探索 1. How many times is the gate of the gate as high as my house? 1. 闸门的高是我家门高的多少倍？ Thirty-eight point five divided by two point two equals to ______ 38.5÷2.2＝________ You can just do it with vertical form. 可以直接用竖式计算。 We'll do it by converting the divisor to an integer. 把除数变成整数就会算了。 Can you calculate 49.5÷0.66 你会计算49.5÷0.66吗？ Forty-nine point five divided by five zero point sixty-six equals to _____ 49.5÷0.66＝_________ Think about it, how do you compute the division of decimals? 想一想，怎样计算除数是小数的除法？
Lesson 3 A box of bacon has eight pieces and cost 97 yuan. 一盒腊肉有8块，花了97元。 I bought six boxes of tea, which cost 350 yuan each. 我买了6盒茶叶，一个花了350元。 What questions can you ask? 你能提出什么问题？ Cooperative exploration 合作探索 How much is the bacon per slice on average? 1. 平均每块腊肉多少钱？ Ninety seven divided by eight is approximately equal to _______(yuan ) 97÷8≈________(元) When counting money, two decimal places or one decimal place are usually reserved to indicate accuracy down to minutes or corners 计算钱数时，通常保留两位小数或一位小数，表示精确到分或角。 In general, the "rounding- off" method is used to find the approximate value of 一般情况下，要用“四舍五入法”求出上的近似值。 How much is the average box of tea? 2. 平均每盒茶叶多少钱？ Three hundred and fifty divided by six equals to fifty-eight point three three three……(yuan) 350÷6＝58.333....(元) Can you calculate 63÷22 and 8.05÷3.7 你会计算63÷22和8.05÷3.7吗？ The number of decimal places in the fractional part is a finite decimal, which is called a finite decimal. For example: 12.125. 小数部分的位数是有限的小数,叫作有限小数。例如:12.125。 The number of digits in the decimal part is an infinite decimal, called an infinite decimal. For example: 3.181818... . 小数部分的位数是无限的小数,叫作无限小数。例如:3.181818…。 Like 58.3333... , 2.86363... , 2.1756756... The sequence of one or more digits starting with a certain digit .A decimal that repeats itself is called a repeating decimal. 像58.3333…,2.86363…,2.1756756…,小数部分从某一位起,一个数字或者几个数字依次不断地 重复出现,这样的小数叫作循环小数。
Lesson 4 The Three Gorges is magnificent! 三峡大壮观呀! Last year, during the "National Day" Golden Week, Shancheng Travel Agency had a total income of 525,000 yuan, and Sunshine Travel Agency a total income of 476,000 yuan. 去年“十一”黄金周期间,山城旅行社共收入52.5万元,阳光旅行社共收入47.6万元。 What questions can you ask? 你能提出什么问题? Cooperative exploration 合作探索 1. During the Golden Week, how much more does Shancheng Travel Agency earn than Sunshine Travel Agency every day on average? 1. 黄金周期间,山城旅行社平均每天比阳光旅行社多收入多少万元? First calculate fifty two point five minus forty seven point six,and then divided by even (52.5－47.6)÷7 A: the average daily income of shancheng travel agency is ______ million yuan more than that of sunshine travel agency. 答:山城旅行社平均每天比阳光旅行社多收入______万元。 The sequence of integer mixed operations also applies to decimal operations. 整数四则混合运算的运算顺序对于小数运算同样适用。
Clever surveyor 聪明的测量员 Around us, there are some special objects whose length, mass, area and so on are difficult to measure directly.For example, the area of the mesh of a mosquito net, the thickness of a page of a dictionary, the diameter of a piece of copper wire and the mass of a grain of soybeans. 在我们身边,有一些特殊物体,它们的长度、质量、面积等是很难直接测量出来的。例如蚊帐网眼的面积、词典一页纸的厚度,一根铜丝的直径和一粒黄豆的质量等。 Develop a program 制订方案 The area of a net on a mosquito net How should the area of the net be measured? 蚊帐上一个网眼的面积帐的面积该怎样测量呢？ The net's mesh area is too small to be measured directly. 蚊帐的网眼面积太小了,无法直接测量。 I know the story that cao chong says elephant, can pass the method of transformation...... 我知道曹冲称象的故事，能不能通过转化的方法...... You can draw a small piece out of it, measure its area, and divide by the number of mesh...... 可以从中划出一小块，测量出它的面积，再除以网眼的个数...... Some of the tools you'll need are a ruler, a calculator, and the design of a logging chart. 需要到的工具有:尺子、计算器,还要设计一个探究记录表。 I tried to measure the thickness of one page of the dictionary. 我想办法测量词典一页纸的厚度。 Practical inquiry 实践探究 I first measure the area of a small rectangular mosquito net...... 我先测量出一小块长方形蚊帐的面积...... Weigh out 10 grams of soybeans and...... 称出10克黄豆的质量，再...... Measure out the copper coil...... 量出铜线圈...... Measure the total thickness of the dictionary first... 先量出词典总的厚度…… Display and exchange 展示交流 Inquiry record sheet 探究记录表
Retrospection and reflection 回顾反思 I found that many objects can be measured with the help of "Cao Chong weighing the image" method.
Powered by Discuz! X3.4 Copyright © 2001-2020, Tencent Cloud. |
