Teaching objectives:
1. Make students understand the quantitative relationship of practical problems such as "How many" in specific situations and calculate them correctly.
2. Enable students to find and put forward the actual problem of "how much is it" in life and solve it effectively, and cultivate students' problem consciousness and mathematical communication ability.
3. Let students develop the habit of marking units when solving practical problems in writing; Let every student get a successful experience and enhance their interest and self-confidence in mathematics learning.
Teaching emphasis: understand the quantitative relationship of practical problems such as "how much is it" and calculate it correctly.
Teaching difficulties: understand the meaning of the question, find the quantitative relationship and determine the method of solving the problem.
Teaching process:
First, the new curriculum exploration
1. Interesting lead: Our good friend Xiaoduoduo, a freshman, is in a hurry. She is in trouble. Let's help her.
parsing problem
(1) Show the first message in the example: What information do you know from the picture? How many trees may there be? (There must be at least 23 tour guides) Q: Is it possible to have 20, 15? Why? Read "five lefts" and problems.
(2) Explain what "original" means (animation demonstration returns 23 peaches to the tree)? How many parts are there in the peach on the tree? How to find the original peach? Talk to each other at the same table (guide the students to combine the picked peaches with the remaining peaches)
solve problems
(1) refers to column type calculation. According to the students' answer on the blackboard: 23+5=28, let the students answer what 23 means. (Health: 23 means that the little monkey picked 23 peaches) Post a blackboard book: What does 5 mean when it is picked? Stick it on the blackboard: The rest, what does 28 mean? Stick it on the blackboard: Originally, the teacher asked: Why do you use addition? Lead the students to say: If you want the original peaches, you should combine the picked peaches with the remaining peaches.
(2) Introduce some unit names: use multimedia to show formulas and find out the differences from the blackboard. The students found an extra "elder brother". Introduce "Ge" as the unit name to guide students to find out the conditions and problems. Explain that appropriate units should be added after the formula when solving problems.
(3) Introduction A: What is the problem? How to answer is to turn how much you don't know in the question into a calculated number.
Second, consolidate the practice.
1. Basic exercises
(1) Creating a Situation1-Problems in the Mystery of Wisdom Paradise. (Show the courseware) What are the known conditions? Guess what the caterpillar teacher will ask? (Ask your own questions) and then answer them independently. After the students finish, tell me how you calculate continuously. Why are you doing this? (The introduction says that a * * * puzzle is divided into two parts, one part has been put together, and the other part has. Combine the two parts to find a * * *. ) Post a blackboard book (quantitative relationship) according to the students' answers to remind the final inspection unit and answer in parallel.
(2) Creating Situation 2-Problems in Happy Paradise. The farm is harvesting cabbage. Let's read the known conditions and problems. Judging by two different answers designed by Jiang Mingming and Xiao Duoduo, talk about why, and let the students clearly ask for the original number. The number of a * * * cannot be subtracted, so we should think backwards, add up the collected and non-collected trees, and find a * * * 50 trees.
2. Summary
Q: We solved three problems just now. What method did we use? Why? (Guidance: Everyone requires a * * *) Teacher's guidance: We can say that we have removed the selected, spelled and collected, and the rest can be said to be left over. Use the deleted number+the remaining number is equal to the original number of a * * * (display cardboard sticker). This is the practical problem of finding the original number (showing the board) that we are going to learn today.
3. Consolidate and improve
(1) Comparison exercise. Show it and think about the fourth question (1). The teacher reads the questions, then asks the students to read them, and then finishes them independently. Tell me your speech. Why? Show (2) again, read the questions and talk about how to calculate continuously. Contrast: It's all about how many there are now, and why the above questions are added and the following questions are subtracted. (The first question that leads students to say is how much now refers to a * * *, and the second question is how much now refers to how much is left now. ) it shows that the two problems are similar, but the methods are different. When solving problems, we must use our brains and think hard.
(2) Hide conditional exercises. Situation to create small blossoming topic: _ _ _ _ _ _ _, I ate four, and how many apples did my mother buy? According to the blackboard, what are the known conditions and problems, and what are they missing? Find out the hidden conditions in the diagram, then read and calculate in parallel. (The guide adds the deleted number and the remaining number to make it equal to a * * * number.)
(3) make up your own questions.
A, courseware demonstration: 10 The bird flew away from the tree, _ _ _ _ _ _, how many are there in the tree? Look for numbers according to the sticker. What is missing? Then show two conditions: 10 left and 10 left. Ask the students to choose and explain the reasons, and then calculate.
B, _ _ _ _ _ _ _ _ _ _, there are 10 books left on the shelf. How many books are there? Read it quietly and tell me what you know. What number is missing? Students discuss, add a condition, and calculate according to the conditions added by students.
Third, review and summary:
Teacher: What did we learn today? (Find out what the actual problem is)
Teacher: How to solve this problem? (The introduction divides the original or a * * * number into two parts, one part is the removed number, and the other part is the remaining number. Require the original number or * * * number to add the removed number and the remainder. Don't forget to add the name of the company when solving the problem.
Reflection after teaching:
"How many practical problems are there" is actually a problem of "seeking the minuend", which is often encountered in daily life. It is a reverse thinking to solve the remaining practical problems, and it is essentially a summation problem considered from another angle. Students have some difficulties in learning the content of this course. Considering these factors, I rearranged the teaching materials, so that students can fully understand the quantitative relationship of such problems in certain situations and cultivate their mathematical thoughts through different levels of practice.
1. Create a situation to stimulate interest.
Interest is the best teacher and a great motivation to acquire knowledge. The example of this lesson is a little monkey picking peaches, and most of the exercises are in real life. The textbook itself has taken into account the age characteristics of students and linked mathematics with life. However, in order to arouse students' interest, I got to know them better and found that their favorite is Xiao Duo Duo and the caterpillar teacher in Grade One. So I took this as the main line, and the caterpillar teacher took them through Xiaodiduo's discovery after class, Xiaodiduo learned to use knowledge and so on, so that students were always in the story. Therefore, from the beginning to the end of the class, the students have been in a relatively excited state.
2. Explore independently and cultivate awareness (ask questions, analyze problems and solve problems).
Strong curiosity and thirst for knowledge are children's nature and the driving force of inquiry activities. When teaching examples, I asked the students to guess how many peaches there might be on the tree, and set a question: "Is it possible to have 20, 15" to help the kids explain the meaning of "original", and returned the picked peaches to the tree through animation demonstration, which greatly increased the students' awareness of inquiry. Next, the students discuss how to find the original number and realize how to use the picked peaches through communication. When talking about the meaning of each number in the formula, students can understand and solve problems by communicating why addition is used, and in the process of mutual inspiration and independent thinking. In the future practice, I fully respect students' opinions, let them read questions, ask questions and ask conditions independently, and gradually cultivate their consciousness of asking questions, analyzing problems and solving problems.
3. Practice in layers to improve thinking.
Happy classroom requires teachers to carefully design layered exercises suitable for each student's development according to different students, so that each student can practice in class and test the effectiveness of learning. Put an end to one-size-fits-all mechanical exercises, consolidate knowledge and ability in diversified and multi-level exercises, cultivate good thinking ability and enrich students' experience. Therefore, there are various forms of practice in this class, such as answering independently, judging right or wrong, selecting conditions, filling in conditions independently, etc. Stimulate students' thinking from a variety of practice angles. The exercise content is divided into three levels: basic exercise, comparative exercise and supplementary condition exercise. These different forms and levels of exercises enable students to improve their thinking and experience the happiness of learning success in the process of self-dialogue and communication.
Most of the children in this class have mastered the ideas and methods to solve such practical problems, and they are very interested, but a few introverted and timid children have been ignored by me and have no time to correct their mistakes on the spot. How to express the thinking of solving problems in language needs further training. In addition, students don't understand the quantitative relationship very well. For example, when choosing conditions, although many students have made analysis, they still made the wrong choice. In the future class, I will continue to cultivate children's ability in this respect, pay as much attention to every student as possible, so that every student can get a balanced development.