subtraction 3 digit regrouping

The following is a reflection on the two-digit by two-digit problem solving event: ** 1. Knowledge Understanding and Usage ** 1. ** Mastery of Arithmetic ** - Arithmetic was the key to multiplying two digits by two digits. For example, splitting two-digit numbers into tens and one-digit numbers, multiplying and adding them, students might not understand the problem thoroughly when solving it. This could lead to calculation errors or incorrect formulas in practical applications. If the students found it difficult to understand mathematics during the activity, it might be because there were not enough examples in the teaching process for the students to explore the nature of mathematics. 2. ** Proficiency of calculation method ** - The calculation method of multiplying two digits by two digits included the steps of digit alignment, first multiplying by one digit, then multiplying by ten digits, and finally adding them up. When solving problems, students might spend too much time or make mistakes because they were not familiar with the calculation method. This reflected that there might be a lack of practice or targeted practice in the teaching before the event. For example, if a student was not familiar with rounding, it would be easy to make a mistake when solving a practical problem such as " a set of uniforms costs 32 yuan, and there are 45 students in the class. How much does it cost to buy a uniform?" ** 2. Ability to solve problems ** 1. ** Problem analysis ability ** - When encountering practical problems related to multiplying two-digit numbers by two-digit numbers, students needed to accurately analyze the relationship between the numbers in the problem. Some students might rush to calculate the problem without thinking carefully about the meaning of each number. For example, in the question " There are 23 boxes, and there are 12 apples in each box. How many apples are there in total?" If the student could not correctly determine that 23 and 12 were the number of boxes and the number of apples in each box respectively, they would not be able to give the correct calculation. This might be due to the lack of specialized training in problem analysis in the usual teaching. 2. ** The variety of solution strategies ** - When solving the problem of multiplying two digits by two digits, in addition to the conventional calculation method, one could also use estimation and other strategies. However, students may only rely on pen calculations during the activity and will not flexibly use estimation to quickly determine the approximate range of the results. For example, if a student were to judge whether the product of 28×19 was greater than 500, they could quickly come to a conclusion if they could first estimate that 28 was close to 30, 19 was close to 20, and 30×20 = 600. However, many students might not have the awareness of this solution strategy. This showed that there was not enough emphasis on the variety of problem solving strategies in the teaching. ** 3. Teaching guidance ** 1. ** The effectiveness of situation creation ** - If a relevant problem situation was set up in the activity, the rationality and effectiveness of the situation would have a great impact on the students 'solution to the problem. If the situation was too complicated or detached from the student's reality, it would increase the difficulty of the student's understanding of the problem. For example, creating a situation about two-digit multiplying two-digit numbers in ancient business transactions might be difficult for modern students to understand, but if they created a situation that was close to life such as shopping, class size, and item distribution, it would be easier for students to understand and solve the problem. 2. ** Guiding the students 'thinking ** - In the process of students solving problems, the teacher's guidance was crucial. If the teacher did not give appropriate hints and guidance when the student made a mistake or was stuck in thought, it might cause the student to be unable to solve the problem smoothly. For example, when a student was calculating 25×16, if it was difficult for the student to calculate it using conventional methods, the teacher could guide the student to split 16 into 4×4 and then use the special calculation of 25×4 = 100 to simplify the calculation. However, if the teacher did not have such a guiding consciousness, the student might go further and further on the wrong calculation method. ** 4. Students 'study habits ** 1. ** Habit of seriously examining questions ** - Many students didn't have the habit of seriously examining the questions when they were solving the problem of multiplying two digits by two digits. They might ignore key information in the question, such as "about","how much more","how much less", etc., which would lead to mistakes in solving the question. For example, the question was " 18 school bags, each bag is 22 yuan, how much is it?" If the student did not pay attention to the " about " and did an accurate calculation, it would not meet the meaning of the question. This reflected that in the usual teaching and learning process, there was no emphasis on cultivating the habit of students to seriously examine questions. 2. ** Writing standards and checking habits ** - Two-digit multiplied by two-digit calculations required a standard writing format. During the activity, some students might be found to have irregular writing, which not only affected the accuracy of the calculations, but also was not conducive to subsequent checks. Moreover, many students did not have the habit of checking their calculations after they were done, so they could not find their mistakes in time. This might be because there was no strict requirement and continuous training for writing norms and checking habits in the teaching. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>

Once upon a time, there was a farmer who had 20 sheep. One day, 8 sheep got lost. We can write this as a subtraction story: 20 - 8. To find out how many sheep are left, we start with 20 and take away 8. We can break 20 into 10 and 10, and 8 into 5 and 3. First, take away 5 from one of the 10s, we get 5 left in that part. Then take away 3 from the other 10, we get 7 left in that part. So in total, there are 12 sheep left.

There were a few points worth reflecting on in the teaching of deduction: 1. ** Arithmetic understanding **: When the students are asked to work together in small groups to self-study the calculation of deduction based on their existing addition calculation methods, although the students can come up with a variety of methods and participate actively, if the teacher does not emphasize the relationship between minuend, reduction, and difference enough, it will cause students to make mistakes such as using reduction to reduce difference or difference to reduce reduction. This shows that a thorough understanding of the calculation theory is crucial. 2. ** Teaching arrangement **: For example, the addition and deduction calculation is divided into two classes because students made more mistakes when doing addition and deduction homework. In the teaching of addition calculation, by adding review questions to pave the way for new knowledge, students could be motivated. Students could also quickly discover the calculation method, and they could also use the student's name to increase their participation. However, if only the addition calculation was taught, the amount of practice in the classroom might not be enough, and the slow calculation speed of the students would affect the practice density. 3. ** Overall teaching planning **: You need to understand both the teaching materials and the students. The life situations in the teaching materials (such as the scene of buying things containing addition and substitution problems) could be used to introduce new lessons and lead to verification teaching. At the same time, they had to make clear the teaching objectives (such as letting students learn the calculation method of addition and deduction, developing the habit of checking, improving the accuracy of calculation, etc.), the key points (addition and deduction checking), the difficult points (the variety of checking methods), prepare the teaching aids, and also consider how to take care of the poor students, design the teaching links (knowledge laying, questions, homework, knowledge extension, etc.). 4. ** Teaching Method **: The teacher should not talk too much. The classroom should be returned to the students so that the students can learn the knowledge of deduction calculation through self-study and exploration. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>

In the teaching of two-digit minus one-digit abdication, there are the following points worthy of reflection: ** 1. Grasping the student's basic knowledge ** 1. ** Using existing knowledge ** - Before the students learned two-digit minus one-digit abdication, they had already mastered the abdication of less than 20, two-digit plus one-digit, and tens, two-digit minus one-digit non-abdication, and tens. In teaching, we should make full use of this existing knowledge and guide students to learn new content through knowledge transfer. For example, when faced with a question like 36 - 8, the student could recall the situation where 6 - 8 was not enough to reduce the number within 20, and then think about how to solve a similar problem in two-digit numbers. 2. ** The impact of differences in knowledge base on teaching ** - There were differences in the degree of mastery of previous knowledge between students. Some students did not have a solid grasp of abdication within 20, which would lead to difficulties when calculating two-digit minus one-digit abdication. For example, the calculation speed was slow and error-prone. This requires teachers to pay attention to this difference in the teaching process and provide targeted guidance to these students. ** 2. Teaching methods ** 1. ** Diverse algorithms and understanding of arithmetic ** - In teaching, it is important to encourage students to calculate in a variety of ways. For example, for 36 - 8, students might have 36 - 6 - 2 = 28, divide 36 into 20 and 16, calculate 16 - 8 = 8, then 20+8 = 28, or divide 36 into 10 and 26, calculate 10 - 8 = 2, then 26 + 2 = 28, etc. However, in this process, although there were various algorithms, students might not be able to express the algorithm clearly, especially when it came to middle and lower physiological solutions. Teachers needed to guide students to explore various algorithms, but at the same time, they needed to pay more attention to letting students understand the calculations behind each algorithm, such as the meaning of borrowing. 2. ** Operation and Practice Section ** - Placing sticks was an effective way to help students understand arithmetic. However, there might be problems in practice. For example, the teacher did not let the students prepare the learning tools (sticks) in advance, and did not let the students count the sticks in advance, which led to the waste of time in the classroom. Moreover, when the students placed the sticks, some teachers only asked the students to talk about the process of placing the sticks, but ignored the practical process of letting the students go to the stage to show how to take 8 sticks out of 36 sticks. This was not conducive to the students 'in-depth understanding of mathematics. 3. ** Teaching Quick Calculation Skills ** - Subtracting a two-digit number from a one-digit number had a quick calculation trick, such as adding 1 when minus 9, adding 2 when minus 8, and so on. However, if one only focused on imparting quick calculation skills in teaching, and the students did not understand its essence (the essence was to break the ten methods), it might cause the students to memorize it mechanically and not be able to use it flexibly. The teacher should emphasize the connection between speed calculation and arithmetic while explaining the skill. ** 3. Cultivating students 'abilities ** 1. ** Cultivation of the ability to express oneself ** - In the teaching process, we should pay attention to cultivating students 'ability to express themselves. Students could only clearly describe the calculation method and process after they understood the calculation theory. For example, in the calculation process of 36 - 8, students should be allowed to explain the calculation process more often. This would help them think clearly and allow teachers to better understand the students 'mastery. 2. ** Cultivating Awareness of Independent Exploration and optimization of algorithms ** - It was necessary to guide students to carry out independent and exploratory learning and cultivate their good learning habits. After the students explored a variety of algorithms, the teacher should organize the students to compare these algorithms, guide the students to optimize the calculation method, and enhance the awareness of the optimization algorithm. For example, students could compare the difference in calculation speed and accuracy of different algorithms to choose the algorithm that was more suitable for them. ** 4. Pay attention to students of different levels ** - In classroom teaching, not only should we pay attention to cultivating students 'creative expression ability, but we should also pay attention to the learning mastery of the backward students. Teachers could not only focus on some of the positive students, but should focus on every student, discover and correct the students 'mistakes in time, so that every student could experience the joy of success, and ensure that all students could better master the mental arithmetic method of two-digit minus one-digit abdication. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>

The following is a possible reflection on the teaching of continuous substitution: ** I. Teaching of calculation methods and students 'mastery of them ** 1. ** Calculation accuracy and speed ** - When teaching continuous substitution, it was similar to abdicating within 20. Some students might have problems with slow calculation speed or insufficient accuracy. For example, for a three-digit substitution with continuous abdication, like 435 - 276, students might make calculation errors during the calculation process due to the complexity of abdication. This might be because they didn't have a good understanding of the calculation of abdication. For example, if 5 minus 6 wasn't enough, they had to retreat from 10 to 10, add it to the single digits, and then subtract. If 2 minus 7 wasn't enough, they had to retreat from 100 to 10. This series of calculations was not well understood, resulting in confusion. - In the teaching, although conventional methods such as vertical calculation were taught, some students might still be used to calculating in their own way. For example, there might be situations like counting fingers in the abdication of the number within 20. This reflected that the teaching method might not be fully adapted to the learning habits of all students. It was necessary to further explore how to guide students to master more efficient and accurate calculation methods. 2. ** The application of different calculation methods ** - There might be many calculation methods for continuous substitution. For example, for three-digit substitution, in addition to vertical calculation, students might also be guided to use methods such as number decomposition to calculate. However, during the teaching process, it might be found that students 'acceptance of different methods was different. Some students might prefer the more intuitive method of vertical calculation, but they might have difficulty understanding and applying other methods. This required thinking about how to balance the teaching of multiple calculation methods so that students could choose the appropriate method according to different topic situations. ** 2. Students 'performance in solving problems ** 1. ** Comprehension of the question ** - Students might not be able to understand the meaning of the questions in the application questions involving continuous substitution. For example, in a continuous deduction application question written according to some actual scenarios, such as the number of crops planted, the number of insects, etc., the student might have difficulty accurately determining which numbers have a deduction relationship, and thus list the wrong calculations. This might be because there was too much information in the questions, and students lacked the ability to extract key mathematical information from complex information. 2. ** Judgement of operational relationships ** - When students were solving problems, they would sometimes confuse the relationship between addition and substitution. For example, in some questions that required continuous deduction to get the answer, addition might be used incorrectly. This reflected that the students did not have a deep understanding of the significance of deduction in practical problems. They needed to strengthen it through more examples in teaching. ** 3. Other problems in the teaching process ** 1. ** Thought Guidance ** - When he was teaching the continuous deduction, he might not have fully explored the depth of the students 'thinking. For example, when guiding students to discover the rules in the continuous deduction formula, they might only be limited to the conventional observation direction, such as calculating from left to right in order. They were not guided to observe and think from different angles, such as the difference law between numbers and the change law of numbers on the digits, which was not conducive to cultivating students 'scattered thinking. 2. ** Use of teaching tools and resources ** - In the teaching process, the use of teaching aids (such as counters) or multi-media resources (such as coursewares) may not be sufficient or reasonable. For example, when explaining the continuous abdication process, the counter could have shown the abdication process very well, but it might not have played its full role in teaching, causing some students to have difficulty understanding the abstract concept of abdication. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>

The use of a 6-digit code in manga can vary. It could be for accessing bonus chapters, redeeming rewards, or verifying your identity as a subscriber. You might need to enter it in a designated area provided by the manga platform.

One digit success story could be the rise of digital payment platforms like PayPal. It revolutionized the way people transfer money online, making it fast, secure and convenient for both individuals and businesses. It started small and grew exponentially, now being used worldwide.

I had 50 dollars. I spent 20 dollars on a book. So the subtraction story is 50 - 20 = 30. I have 30 dollars left.

It makes subtraction more interesting. Instead of just looking at numbers, students get to engage with a story, which is more fun. For example, a story about sharing toys can show subtraction in a natural way.

The four-digit number representing safe entry and exit was 1483. The number 1 represented one, the number 4 represented the world, the number 8 represented peace, and the number 3 represented peace. These four numbers combined represented peace. Watching " Safe Entry " wasn't enough. Everyone, please click to read the novel!