Decimal division unit mainly enables students to master the following knowledge:

1. Calculation method of fractional division

The first category: fractional division with integer divisor.

Methods: According to the method of integer division, the decimal point of dividend was aligned with the quotient decimal point.

The second category: fractional division with divisor as decimal.

Methods: Using the law of high invariance, the divisor was converted into an integer, and then calculated according to the first method.

2. This unit should strengthen the training of division calculation and do 10 written division questions every day. In particular, we should strengthen the division of quotient plus 0. For example, the answer to 4872÷24 is 103, and students easily forget to add 0 to become 13.

3. The approximate number of quotient is not difficult, as long as students remember to divide by one more than the reserved number.

4. The number divided by less than 1 will become larger, and the number divided by more than 1 will become smaller.

This rule is something that every student must master.

5. The change law of quotient is also very important: the dividend is constant, and the divisor is expanded or reduced several times, but the change of quotient is just the opposite.

If the divisor remains the same, the dividend will expand or shrink several times, and the quotient will also expand or shrink several times.

6. Classification of decimals: 1. Finite decimal 1. Pure cyclic decimal.

2. Infinite decimal: 1. Cyclic decimal: 2. Mixed cyclic decimal.

2. Do not cycle decimals

Infinite decimals are divided into cyclic decimals and acyclic decimals.

Circular decimals are divided into pure circular decimals and mixed circular decimals.

7. In the representation method of cyclic decimals, it is easy for students to make mistakes by asking them to do calculations and then using cyclic decimals to represent the answers.

For example, the answer to 22÷7 should be 3. 142857 is a cycle of 142857, which students can easily express as142857/.

8. This unit should also let students know when to use the memorization method and when to use the memorization method.

One-step method (loading, laying floor tiles, etc.). )

Refund (buy things with money, divide things, etc.) )

9. After learning fractional division, students often don't know which one to divide.

For example, 10 yuan bought eight sweets.

10÷8 means how much is each candy?

8÷ 10 means how many sweets can you buy for one dollar? (Let the students distinguish)

Reflections on the teaching of fractional division unit

The unit "Division of Fractions" is unfamiliar to students, so we dare not slack off in the teaching of this unit. First of all, I read through this textbook, and then look at the faculty and staff carefully against the textbook. Then, I analyzed the relationship between this unit knowledge and the old knowledge, carefully compared the similarities between fractional division and integer division, and the knowledge base and ability base of our classmates. Attention should be paid to arousing students' positive memory of integer division calculation methods in class and strengthening the comparison between integer division and decimal division; Pay attention to the problems in real life, create some realistic situations, and improve the mastery of calculation methods in solving problems. I analyzed the students' exercises, and found that the problem that students made more mistakes was mainly the division by adding "0", which was originally caused by "0". Think carefully about these troubles caused by 0, the main reasons are as follows: First, students have not laid a good foundation for integer division and practiced less, which may be the negligence of previous teaching. Second, there is an understanding of arithmetic in class, but not enough attention is paid to it. It is necessary to draw more students and communicate the meaning of each step in the vertical form. The understanding of arithmetic is only done well in the first class, and it is weakened in the following classes, resulting in students' poor understanding. Third, some students have poor study habits and are always forgetful when doing problems. They either forgot to enter the decimal point and the quotient 0, or forgot to expand the dividend and divisor by the same multiple at the same time. Fourthly, there are few exercises in the arrangement of teaching materials and supplementary questions after class, and students' computing ability is not strong, especially at the beginning of the curriculum reform, the supplementary exercises after class are almost zero, which has caused the trouble of "0" now.

After realizing this, my teaching suggestions for this part of knowledge are as follows: first, compare these types of questions with "0", summarize their similarities and differences, distinguish the different meanings of 0 in each category, and establish the impression of different meanings of 0 in students' minds; The second is to strengthen the understanding of arithmetic, so that students can talk about the reasons for each step of calculation every time they finish a problem, which means how much is divided by how much, or how much is divided by how many tenths. Third, let students check as much as possible in order to check their own calculation errors better; Fourth, increase the practice of calculation, and add some calculation problems to students in class, which not only achieves the effect of training calculation ability, but also enhances the interest of class; Fifth, give play to the mutual help of peers, especially the mutual help among students in the group. First of all, they can compete with each other and learn from each other at the same time, which also reduces the burden on teachers and promotes the progress of the whole class. It also made me understand that in teaching, our teachers can't look at problems from the perspective of adults and ignore some details. We should think more from the students' point of view, fully estimate the problems that students may have in the learning process, respond flexibly and take corresponding measures to remedy them. I think this really explains the connotation of teachers' roles of "organizer, guide and collaborator" advocated by the new curriculum.

The calculation teaching of decimal multiplication and division plays a very important role in the fifth grade, but the error rate of students is very high, and there are many kinds of errors, even the simplest addition and subtraction. Even if students are repeatedly advised, these mistakes will still appear. Investigate its reason, there should be two problems.

First, the knowledge points are not firmly grasped. It may be that the basic concepts and arithmetic are not clear, or it may be oral calculation.

If the calculation with a pen is not accurate, the calculation will be full of mistakes.

Second, it should be students' psychological reasons. Students often use the word "carelessness" to explain the mistakes in calculation, but apart from the mistakes caused by poor study habits, more are psychological reasons.

Teachers need to organize multi-level, multi-faceted and multi-form exercises in order to let students master the mathematics knowledge related to calculation.