The teaching goal of writing division, the second volume of the fourth grade of People's Education Press;
1, so that students can master the writing position of quotient divided by integer decimal.
2. Cultivate students' generalization and reasoning ability, and understand that divisor is the division operation of two digits.
3. Cultivate students' sense of participation, stimulate students' inductive reasoning ability, and apply what they have learned to solve simple practical problems.
Teaching emphasis: determine the writing position of quotient.
Teaching difficulty: how to determine the writing position of quotient?
Teaching process:
First of all, ask questions:
1. Last class, we learned oral arithmetic in which the divisor is an integer ten. We do a set of oral arithmetic problems, which require us to look at the problems first and then calculate.
60? 30= 120? 20=
160? 80= 240? 30=
350? 50= 270? 30=
Students have a solid grasp of arithmetic. Let's do one more thing to solve problems in life with mathematical knowledge:
There are 92 comic books in the school, which will be distributed to three classes. How many people are there in each class?
Divider is a one-digit pen division. How to calculate, what should I pay attention to?
Try to divide the first digit of the dividend by the divisor. If the first digit is less than the divisor, divide the first two digits.
Write the quotient except the dividend on the dividend.
Write the quotient except the dividend on the dividend.
The calculation method of pen division with divisor of one digit is also suitable for pen division with divisor of two digits. We will explore this lesson.
3. Reveal the learning objectives:
Understand and master divisor is the arithmetic and trial-and-error method of integer decimal pen division, and can correctly write the position of quotient.
Second, solve the problem:
1, when we communicate before class, we designed a practical problem that divisor is an integer real number in life before class. Let's discuss in groups and choose the questions that your group is most interested in. The teacher chooses a whole class from the problems you choose to solve.
Shentong Express Company has 94 mails and 30 people deliver them. How many pieces does each person send?
Look at the formula, think about it first, what is the quotient of 94 divided by 30? Can you find a way to solve it with the knowledge we have learned before? If you encounter difficulties, you can draw a point with a stick figure, and then communicate in the group when you think about it.
How did you solve it?
Should quotient 3 be written in one place or ten places? Why?
Now let's compare. Divider is a pen division of a number. When dividing, let's look at the first digit of the dividend. What about pen division where the divisor is a two-digit number?
Why not look at the top of the bonus first?
9 means 9 tens, and 9 tens divided by 30 is not enough quotient 1 tens. Look at the first two digits of dividend, 94 1 divided by 30, and the quotient is 3 1. Except for one digit, all businesses write in one digit.
In the future, we will calculate the divisor into a two-digit pen division, first of all, we must look at the first two digits of the dividend.
2. One more question, teacher. Please help us solve it. Shuang Yan Supermarket in Diaobingshan bought 460 barrels of soybean oil. It sells 30 barrels a day. It will be sold out in a few days.
How to make it? Let's talk together.
What's the difference between these two formulas?
Show self-study tips:
Think about it: what should a quotient be, where should it be written and why? Try independently first, and then communicate in groups.
Student report board performance
Third, summary.
Look at two formulas, the divisor is a two-digit number, the dividend is a two-digit number and one is a three-digit number. What's the difference between writing?
Think for yourself, talk at the same table and write down the results of your communication.
Divider is a written division of two digits. The first two digits of the dividend are not enough to divide, depending on the first three digits.
According to this law, what if the divisor is three digits? Look at the first few numbers. What if the first three digits are not divided enough? See the top few?
Fourth, expand applications.
1. What can I put in the brackets below?
30? ()& lt6 1 20? ()& lt84
40? ()& lt270 60? ()& lt378
70? ()& lt270 80? ()& lt330
2. Mathematics clinic
The car has a weight limit of 60 tons and the goods are 500 tons. How many cars do you need to load?
Step 4 test questions
Reflections on the teaching of pen-based division in the fourth grade of People's Education Press: The pen-based division of two digits divided by one digit is taught on the basis of oral division and vertical division, mainly teaching the arithmetic of dividing one digit by multiple digits, basic operation ideas and vertical writing.
1, vertical writing is a difficult point, and students' existing experience is not enough at this time. So in teaching, most of the time is spent on solving the order of division and vertical writing. Guide to express the process of written division in mathematical language, and let students tell their own thinking process. In order to let students master vertical writing, let students learn first? Say? What can I say to make every student develop? In class, I designed a design. Solitaire asks students to talk about the process of division and written calculation, so as to stimulate each student's enthusiasm for learning and encourage each student? Listen. . Students can write naturally when they say, and know what to do first, then what to do and finally what to do when they do division with a pen. There is a reasonable calculus order.