2. Get the experience of using existing knowledge to solve new calculation problems, feel the internal connection between mathematical knowledge and methods, and cultivate students' ability to transfer analogy and solve simple practical problems.
3. Experience the pleasure of success in independent exploration, cooperation and communication, further establish self-confidence in learning mathematics, and develop positive feelings for mathematics.
4. Understand the teaching focus of "working efficiency × working hours = total workload": summarize and master the written calculation method of multiplying three digits by two digits.
Teaching difficulties: calculate and write multiplication vertical lines correctly and normatively. Teaching preparation: small blackboard, formula patch and other teaching processes: 1. Stimulate students' interest and introduce situations Teacher: Students, do you know what lessons the teacher will give you today? Student: math class, teacher; If you had to choose between Chinese class and math class, which class would you like to take? Student: Little teacher; Some students like math class, while others like Chinese class. In fact, mathematics and Chinese are closely linked. Then let's learn Chinese in math class today, shall we? Health: OK. Teacher: OK, then please take out your Chinese books and open the tenth page of the textbook. Teacher, check your reading. Please read it for a minute. The teacher wants to see how many words each person can read in one minute. (2 minutes) Show the situation according to what the students read 1: Students can read 12 1 words every minute. * * Students have a good habit of reading in the morning. She studied for 23 minutes this morning. Division; Students see this message, do you have any questions to ask? Student 1: * * How many words did the students read this morning? The problem of writing on the blackboard. Teacher: Let's try to list the formulas. The teacher instructed the students to list the formulas. Teacher: OK, let's have a look. Is this a multiplication of several numbers? Let's estimate, how much is it? Please answer. 12 1×23 is about 120×20=2400, (2 minutes) Teacher: Sometimes we have to work out not only the approximate figures, but also the exact answers. Today, let's study the writing method of multiplying three digits by two digits.
Blackboard writing: three-digit times two-digit written calculation. (1 min) Second, solve the problem of writing without multiplication. Master: Students, write down the vertical position first, ok? What should I do if I want to calculate this formula with a pen? No one has studied it, so let me see. The teacher changed him. Can everyone do it? Student: Yes (because students have learned it, they all do the multiplication of two digits by two digits. ) teacher: then let's hurry up and let him. And asked the original board to perform. Please tell the result and be reasonable. Teacher Jia Gai wrote 12 1× 23 = on the blackboard to explain to the students: just now, everyone can calculate a two-digit number multiplied by a two-digit number. Then, let's see how this three-digit number is multiplied by a two-digit number. Let's guess (at the corresponding blackboard, let the students say) and let the students say. The teacher writes on the blackboard. Eat it raw. Teachers and students summarize the calculation method. (8 minutes) Exercise: Choose one of the questions to complete. 213× 31142× 22 (2 minutes) Third, solve the problem of multiplication and carry in writing Teacher: It seems that the students have mastered the method of multiplying three digits by two digits, so let's help Uncle Li solve a problem together. Please have a look. Show me the problem. Teacher: think about it, how to solve it, please list. Student form. Teacher: You see, this is also the formula of multiplying several digits by several digits. I see that some students have long wanted to solve it. Do you have confidence? Student: Teacher: OK, let's count how many baskets of navel oranges Uncle Li has installed. But in the process of calculation, the teacher has three questions. Please pay attention. 1. What's the difference between the calculation and the first formula? 2. What new problems have been encountered in the calculation process? 3. How did you solve the problems you encountered? All right, let's get started. Trial calculation. If you can't solve it, you can ask your deskmate for help. Collective revision. Looking for a problem. Teacher: Students, is this question different from the first one? Health: recite it. Teacher: Let's see how to recite. * * * The reason is the same. Remind students that rounding is an error-prone place in calculation, and everyone should pay attention to it. (6 minutes) Fourth, summarize the calculation method, and compare three digits multiplied by two digits with two digits multiplied by two digits. (Only there are more digits, and the method is the same. Multiply three digits by two digits and ten digits respectively, and then add the results. After the students discuss, the whole class exchanges calculation methods. (3 minutes) 5. Practice calculation. 1. Complete the classroom activities in the textbook. (3 minutes) 2. Discussion: If you encounter such a number, how to calculate it? 3 1× 2 13 5. refining quantitative relations teacher: by solving these two problems, students learned the calculation method of multiplying three digits by two digits. We can also extract quantitative relations from solving these two problems. The words that students read every minute and the number of baskets loaded every day are all work efficiency. Please think about it, what is the quantitative relationship in this topic?
Guide students to draw the following conclusion: work efficiency × working time = total workload.
Teacher: Can you give an example of this quantitative relationship in life?
Student 1: The master makes 20 parts per hour. 1 How many parts do you make at eight o'clock a day?
Student 2: I copy about 12 new words every minute. How many new words can I copy in 20 minutes? (4 minutes) Read the quantitative relationship again to remind students that they can use this quantitative relationship to solve many problems in the future.
Teacher: Next, shall we play games together? Please think of a two-digit number in your mind first, then multiply it by 167, and then add 2500 to the number. Finally, you don't have to tell me all the answers, just tell me the last two digits of the number, and I can guess the two digits you think of right away. Can you believe it? If you don't believe me, let's try.
When teachers and students play games, students will be surprised. If there is enough time, the teacher can tell the students the mystery. 3 minutes)
Seven, summarize the doubts.
Teacher: What useful knowledge have we learned in this class and what problems should we pay attention to? We have learned the method of multiplying three digits by two digits, and we use the method of transferring analogy. In mathematics, this is a useful association and a common way of thinking when we solve problems. So, if you are asked to calculate four digits multiplied by two digits, what do you think? what are you going to do？ Children who are willing to use their brains, please try after class. I think you will find a way. (2 minutes) References:
/qy _ sky/blog/item/a 7216666df279a2a184c74.html I hope I can help you!