Five plus four
Publish: 2021-03-23 14:18:17
1. Computer. (calculation)
attack 25 hit base 0
attack + [
attack main) equipment
attack this / 1 attack = material auxiliary attack
object
defense D assistant
Magic
through attack] according to x
attack object
reason has no essence
its essence
knowledge
Ben +
pieces
equipped with weapon (middle =
Wu
attack quantity base plate n yushiben + F principle (attached
x
+ attack base according to attack)
attack 25 hit base 0
attack + [
attack main) equipment
attack this / 1 attack = material auxiliary attack
object
defense D assistant
Magic
through attack] according to x
attack object
reason has no essence
its essence
knowledge
Ben +
pieces
equipped with weapon (middle =
Wu
attack quantity base plate n yushiben + F principle (attached
x
+ attack base according to attack)
2. Yes, as long as the structure is symmetrical, the load is symmetrical or antisymmetric!
3. Five years of primary school, four years of junior high school.
4. The addition formula is: 5 + 5 + 5 + 5 = 20
the multiplication formula is: 5 × 4 = 20, or 4 × 5 = 20.
hence: D
the multiplication formula is: 5 × 4 = 20, or 4 × 5 = 20.
hence: D
5. In the twinkling of an eye, I taught from grade one to grade four. Every time I finish a unit, I have to do a small exercise. Originally, the problem of hands-on operation has always been a difficult point for students, and they generally do not master it well. This time, however, the reverse happened. Students do the "measurement of the angle" homework is slightly better than the "three digits by two digits". This may have something to do with my usual training of students' practical ability, but at the same time, it makes me realize the importance of calculation again. So, I calm down, decided to improve the students' computing ability to a new height. Through the later training, students seldom make mistakes in unit 5 division by two digits
first, create a situation for students to pay attention to their thoughts and fully realize the importance of calculation.
I created such a situation: "students, have you ever seen building houses“ Some said "yes."“ What should be the first place to build a house? " At this time, basically no one knows. So, I went on to say, "to build a house, you need to build the foundation first." At the same time, with video, let the children know the process of building houses“ What will happen if the foundation is not firmly laid? " Next, a 13 story building under construction collapsed in Jingyuan community on the Bank of Lianhua River in Shanghai on June 27, 2009. After reading, I continued to talk: "students, the consequences of not laying a solid foundation are serious?"“ Serious. "“ In fact, the calculation in our mathematics is the same as that of the foundation. If we don't do the calculation well, our kingdom of mathematics will collapse just like the building in the picture just now. Therefore, we must do the calculation well, so that our kingdom of mathematics will become more and more brilliant. "< The great scientist Einstein said: "interest is the best teacher." It shows that as long as a person has a strong interest in something, he will take the initiative to seek knowledge, explore and practice, and proce ability in the process of seeking knowledge, exploring and practice, so as to turn low efficiency into high efficiency
(1) to stimulate students' interest in calculation by telling stories about mathematicians when they were young
it is almost common for children to like listening to stories. Among them, I told the students a famous story of Gauss hour: one day when school was about to end in the afternoon, many students in a class were not very disciplined. The teacher intended to punish these children gently, so he put forward a question (natural number from 1 to 100): 1 + 2 + 3 + 4... + 97 + 98 + 99 + 100 = (), and then he went home from school“ Students, can you calculate this problem? " Many children shook their heads“ Then let's listen to the story. " The students quickly took out the paper and pen to calculate, but one child did not do it, as if thinking. Soon the child worked out the answer. The method he used is to sum 50 pairs of sequences (1 + 100, 2 + 99, 3 + 98...) of construction sum 101, and get the result: 5050. The child's name was Gauss, and he was only nine years old that year. Later, Gauss became a famous German mathematician, physicist, astronomer, geometer and geodesist. After listening, the students adore Gauss and have a strong interest in calculation
(2) to stimulate students' interest in calculation by using one problem to do more calculation
in the usual calculation teaching, we should be good at training students' computational thinking ability. For example, when learning multiplication and addition calculation in grade two, there is a problem: it's a calculation problem of looking at the diagram, drawing four plates of peaches, six in each of the first three plates, and five in the fourth plate. How many peaches are there in total? Almost all the children are like this × 3 + 5 = 23 × 3 = 18, then 18 + 5 = 23. At this point, I asked, "is there any other algorithm?" The children are trying slowly. Finally, there are children and a new algorithm: 6 × 4-1 = 23 (pieces). If you take the last set as 6, there will be 4 6, and you will get 24. If you calculate one more, you will lose one, and you will get 23. Then, I asked the students to compare, which one is faster? Students quickly understand that the second algorithm is much faster, which stimulates students' interest in computing< Third, strengthen the cultivation of oral calculation ability
the "Primary School Mathematics Syllabus" points out: "to cultivate students' calculation ability, we should pay attention to basic oral calculation training. Oral calculation is not only the basis of written calculation, estimation and simple calculation, but also an important part of calculation ability." If the ability of oral calculation is strong, the speed of written calculation will be fast, and the accuracy of calculation will be improved. From the first grade, we should pay attention to the practice of addition and subtraction. If we can skillfully calculate the addition and subtraction within 20, it will be of great help to the calculation of multiplication and division. For example, when students learn the unit of "three digits multiplied by two digits", some students make mistakes when they encounter this problem: 389 × 28, the first step is 389 × 8 was originally equal to 3112, but some got 3002, 3222... The problem is that 7 + 4 is not right< Fourth, cultivate good habit of calculation.
French scholar Bacon said: "habit is the master of life, people should strive to pursue good habit." So, to some extent, good habits can determine our destiny. Good calculation habits directly affect students' calculation ability. Often some students can correctly understand and master the calculation rules, but they still make mistakes. The main reason is that they don't form a good habit of calculation< In the first grade, I purposely put out a few questions on the blackboard for students to in the book. The students are required to proofread the copied topics carefully, ranging from numbers and symbols, so as to make sure they are good
2. Develop the habit of examining questions
I ask students to see clearly every data and operation symbol in the questions, determine the operation order, and choose a reasonable operation method< (2) develop the habit of checking calculation
I let the students learn the checking method of addition, subtraction, multiplication and division, and make strict requirements on checking calculation as an important part of the calculation process, and advocate using estimation to check the correctness of the answers
in a word, it's not a matter of a day to improve the fourth grade students' computing ability. We should take it as a long-term work. As long as teachers and students make unremitting efforts together for a long time, the students' computing ability will reach a new level.
first, create a situation for students to pay attention to their thoughts and fully realize the importance of calculation.
I created such a situation: "students, have you ever seen building houses“ Some said "yes."“ What should be the first place to build a house? " At this time, basically no one knows. So, I went on to say, "to build a house, you need to build the foundation first." At the same time, with video, let the children know the process of building houses“ What will happen if the foundation is not firmly laid? " Next, a 13 story building under construction collapsed in Jingyuan community on the Bank of Lianhua River in Shanghai on June 27, 2009. After reading, I continued to talk: "students, the consequences of not laying a solid foundation are serious?"“ Serious. "“ In fact, the calculation in our mathematics is the same as that of the foundation. If we don't do the calculation well, our kingdom of mathematics will collapse just like the building in the picture just now. Therefore, we must do the calculation well, so that our kingdom of mathematics will become more and more brilliant. "< The great scientist Einstein said: "interest is the best teacher." It shows that as long as a person has a strong interest in something, he will take the initiative to seek knowledge, explore and practice, and proce ability in the process of seeking knowledge, exploring and practice, so as to turn low efficiency into high efficiency
(1) to stimulate students' interest in calculation by telling stories about mathematicians when they were young
it is almost common for children to like listening to stories. Among them, I told the students a famous story of Gauss hour: one day when school was about to end in the afternoon, many students in a class were not very disciplined. The teacher intended to punish these children gently, so he put forward a question (natural number from 1 to 100): 1 + 2 + 3 + 4... + 97 + 98 + 99 + 100 = (), and then he went home from school“ Students, can you calculate this problem? " Many children shook their heads“ Then let's listen to the story. " The students quickly took out the paper and pen to calculate, but one child did not do it, as if thinking. Soon the child worked out the answer. The method he used is to sum 50 pairs of sequences (1 + 100, 2 + 99, 3 + 98...) of construction sum 101, and get the result: 5050. The child's name was Gauss, and he was only nine years old that year. Later, Gauss became a famous German mathematician, physicist, astronomer, geometer and geodesist. After listening, the students adore Gauss and have a strong interest in calculation
(2) to stimulate students' interest in calculation by using one problem to do more calculation
in the usual calculation teaching, we should be good at training students' computational thinking ability. For example, when learning multiplication and addition calculation in grade two, there is a problem: it's a calculation problem of looking at the diagram, drawing four plates of peaches, six in each of the first three plates, and five in the fourth plate. How many peaches are there in total? Almost all the children are like this × 3 + 5 = 23 × 3 = 18, then 18 + 5 = 23. At this point, I asked, "is there any other algorithm?" The children are trying slowly. Finally, there are children and a new algorithm: 6 × 4-1 = 23 (pieces). If you take the last set as 6, there will be 4 6, and you will get 24. If you calculate one more, you will lose one, and you will get 23. Then, I asked the students to compare, which one is faster? Students quickly understand that the second algorithm is much faster, which stimulates students' interest in computing< Third, strengthen the cultivation of oral calculation ability
the "Primary School Mathematics Syllabus" points out: "to cultivate students' calculation ability, we should pay attention to basic oral calculation training. Oral calculation is not only the basis of written calculation, estimation and simple calculation, but also an important part of calculation ability." If the ability of oral calculation is strong, the speed of written calculation will be fast, and the accuracy of calculation will be improved. From the first grade, we should pay attention to the practice of addition and subtraction. If we can skillfully calculate the addition and subtraction within 20, it will be of great help to the calculation of multiplication and division. For example, when students learn the unit of "three digits multiplied by two digits", some students make mistakes when they encounter this problem: 389 × 28, the first step is 389 × 8 was originally equal to 3112, but some got 3002, 3222... The problem is that 7 + 4 is not right< Fourth, cultivate good habit of calculation.
French scholar Bacon said: "habit is the master of life, people should strive to pursue good habit." So, to some extent, good habits can determine our destiny. Good calculation habits directly affect students' calculation ability. Often some students can correctly understand and master the calculation rules, but they still make mistakes. The main reason is that they don't form a good habit of calculation< In the first grade, I purposely put out a few questions on the blackboard for students to in the book. The students are required to proofread the copied topics carefully, ranging from numbers and symbols, so as to make sure they are good
2. Develop the habit of examining questions
I ask students to see clearly every data and operation symbol in the questions, determine the operation order, and choose a reasonable operation method< (2) develop the habit of checking calculation
I let the students learn the checking method of addition, subtraction, multiplication and division, and make strict requirements on checking calculation as an important part of the calculation process, and advocate using estimation to check the correctness of the answers
in a word, it's not a matter of a day to improve the fourth grade students' computing ability. We should take it as a long-term work. As long as teachers and students make unremitting efforts together for a long time, the students' computing ability will reach a new level.
6. 1、 Basic training:
from the psychological characteristics of different ages of primary school students, the basic requirements of oral arithmetic are different. Low and middle grade students mainly add one or two digits. It is better for senior students to take the one digit by two digit mental arithmetic as the basic training. The specific requirement of oral arithmetic is to multiply the number of one digit and the number of ten digits of two digits, and then add the proct of multiplying the number of one digit and the number of one digit of two digits to the three digits, and quickly say the result. In primary school, this training is a sublimation training of abstract thinking of numbers. It is very beneficial to promote the development of thinking and intelligence
Second, targeted training: the main form of the number of senior primary school students has changed from integer to score. In the operation of numbers, the addition of different denominators is the most time-consuming and error prone place for students, and it is also the key and difficult point of teaching and learning
two fractions, the large number in the denominator is the multiple of the decimal. For example, "1 / 12 + 1 / 3", in this case, oral calculation is relatively easy, the method is: the big denominator is the common denominator of two denominators, as long as the small denominator is expanded by multiple until it is the same as the big number, and the denominator is expanded by several times until it is the multiple of another denominator decimal< Third, memory training
the content of senior calculation is extensive, comprehensive and comprehensive. Some common operations are often encountered in real life. Some of these operations have no specific rules of oral arithmetic and must be solved by strengthening memory training. The main contents are as follows:
1
2. The proct of the approximate value of PI 3.14 with one digit and the proct with several common numbers 12, 15, 16 and 25
3. The denominator is the decimal value of the simplest fraction of 2, 4, 5, 8, 10, 16, 20 and 25, that is, the interaction of these fractions and decimals.
from the psychological characteristics of different ages of primary school students, the basic requirements of oral arithmetic are different. Low and middle grade students mainly add one or two digits. It is better for senior students to take the one digit by two digit mental arithmetic as the basic training. The specific requirement of oral arithmetic is to multiply the number of one digit and the number of ten digits of two digits, and then add the proct of multiplying the number of one digit and the number of one digit of two digits to the three digits, and quickly say the result. In primary school, this training is a sublimation training of abstract thinking of numbers. It is very beneficial to promote the development of thinking and intelligence
Second, targeted training: the main form of the number of senior primary school students has changed from integer to score. In the operation of numbers, the addition of different denominators is the most time-consuming and error prone place for students, and it is also the key and difficult point of teaching and learning
two fractions, the large number in the denominator is the multiple of the decimal. For example, "1 / 12 + 1 / 3", in this case, oral calculation is relatively easy, the method is: the big denominator is the common denominator of two denominators, as long as the small denominator is expanded by multiple until it is the same as the big number, and the denominator is expanded by several times until it is the multiple of another denominator decimal< Third, memory training
the content of senior calculation is extensive, comprehensive and comprehensive. Some common operations are often encountered in real life. Some of these operations have no specific rules of oral arithmetic and must be solved by strengthening memory training. The main contents are as follows:
1
2. The proct of the approximate value of PI 3.14 with one digit and the proct with several common numbers 12, 15, 16 and 25
3. The denominator is the decimal value of the simplest fraction of 2, 4, 5, 8, 10, 16, 20 and 25, that is, the interaction of these fractions and decimals.
7. In the primary school mathematics test questions, the questions involving calculation content account for more than 85% in a test paper. Therefore, it is a very important task for students to strengthen the calculation training and effectively improve the accuracy of calculation. The actual situation shows that the accuracy of a student's calculation is directly proportional to his oral calculation ability. So how to improve the computing power? Please take a look at the following training methods< Basic training
different age of primary school students, the basic requirements of oral arithmetic are also different. Low and middle grade students mainly add one or two digits. It is better for senior students to take the one digit by two digit mental arithmetic as the basic training. The specific requirement of oral arithmetic is to multiply the number of one digit and the number of ten digits of two digits, and then add the proct of multiplying the number of one digit and the number of one digit of two digits to the three digits, and quickly say the result. This mental arithmetic training includes the practice of several spatial concepts, digital comparison and memory training. In primary school, it can be said that it is a sublimation training of abstract thinking of numbers. It is very beneficial to promote the development of people's thinking and intelligence. You can arrange this exercise in two periods. One is to read early, the other is to arrange a group after homework. Each group is divided as follows: one digit is optional, corresponding to the number of one digit or ten digit in two digits. There are 18 questions in each group. Write the formula first, then write the number directly after several times of oral calculation. After a period of time, you will find that your speed and accuracy will be greatly improved< 2. Targeted training
the main form of the number of senior grades in primary school has changed from integer to score. In the number of operations, I believe we do not like the different denominator fractional addition, right? Because it's too error prone. Now, please think for yourself, is the addition (subtraction) method of different denominators only in the following three cases
1. For two fractions, the large number in the denominator is the multiple of the decimal
for example, "1 / 12 + 1 / 3", in this case, oral arithmetic is relatively easy. The method is: the big denominator is the common denominator of two denominators. As long as the small denominator is expanded by multiple, until it is the same as the big number, the denominator is expanded by several times, and the numerator is also expanded by the same multiple, It can be calculated by adding the same denominator fraction: 1 / 12 + 1 / 3 = 1 / 12 + 4 / 12 = 5 / 12
2. The denominator of two fractions is coprime
this kind of situation is more difficult in form, and I believe you are also the most headache, but it can be changed into easy: after it is divided, the common denominator is the proct of the two denominators, and the numerator is the sum of the proct of the numerator of each fraction and the other denominator (if it is subtraction, it is the difference of the two procts), such as 2 / 7 + 3 / 13. The oral calculation process is: the common denominator is 7 × 13 = 91, molecule 26 (2 × 13)＋21(7 × 3) = 47, the result is 47 / 91
if the molecules of both fractions are 1, the oral calculation is faster. For example, "1 / 7 + 1 / 9", the denominator is the proct of two denominators (63), and the numerator is the sum of two denominators (16)
3. Two fractions and two denominators are neither coprime numbers nor multiples of decimals
in this case, we usually use the short division method to get the common denominator. In fact, we can also directly calculate the general score in the formula and get the result quickly. The common denominator can be obtained by enlarging the large number in the denominator. The specific method is: to double the large denominator (large number) until it is a multiple of another denominator decimal. For example, 1 / 8 + 3 / 10 expands the large number 10, 2 times, 3 times and 4 times, and compares it with the decimal 8 every time to see if it is a multiple of 8. When it is expanded to 4 times, it is a multiple of 8 (5 times), then the common denominator is 40, and the numerator is expanded by the corresponding multiple and then added (5 + 12 = 17), and the number is 17 / 40
after reading the above, have you found the rule of mental arithmetic in every situation? So as long as you practice more and master it, the problem will be solved< (3) memory training
do senior students feel that sometimes the calculation content in the topic is very extensive? Some of these operations have no specific rules of oral arithmetic, so I have to solve them through memory training. The main contents are as follows:
1
2. The proct of the approximate value of PI 3.14 with one digit and with several common numbers 12, 15, 16 and 25
3. The denominator is the decimal value of the simplest fraction of 2, 4, 5, 8, 10, 16, 20 and 25, that is, the interaction between these fractions and decimals
the results of the above numbers, whether in daily work or in real life, are used very frequently. After mastering and remembering them, they can be transformed into abilities and proce high efficiency in calculation< 4. Regular training
1. Mastering the law of operation. There are mainly five laws in this aspect: commutative law and associative law of addition; Commutative law, associative law and distributive law of multiplication. Among them, the multiplication distribution law is widely used and has many forms, including positive use and negative use, and the forms of integer, decimal and fraction. In the multiplication of fractions and integers, we often ignore the application of the law of distribution of multiplication, which makes the calculation complicated. Such as 2000 / 16 × 8. If we use the law of multiplicative distribution, we can calculate the result of 1000 by mouth directly. But if we use the general method of recing false fraction, it is time-consuming and easy to make mistakes. In addition, there are subtraction properties and quotient invariant properties< 2. Regular training. It is mainly the oral calculation method of the square result of the two digit number of 5
3. Master some special cases. For example, in fractional subtraction, if the numerator is not enough to be subtracted after general division, and the numerator subtracted is usually larger than the numerator subtracted by 1, 2, 3 and other smaller numbers, no matter how big the denominator is, it can be directly calculated orally. For example, the difference between 12 / 7 and 6 / 7 is only 1. The difference between 12 / 7 and 6 / 7 must be 1 less than the denominator. The result is 6 / 7 without calculation. Another example is: 194 / 99-97 / 99, if the difference between the numerator and denominator is 2, the difference between the numerator and denominator is 2, and the result is 97 / 99. When the subtracted molecule is larger than the subtracted molecule by 3, 4, 5 and other smaller numbers, the result can be quickly calculated orally. Another example is the mental calculation of the proct of any two digit number and 1.5, which is two digits plus half of it< 5. Comprehensive training
1
2< 3. Comprehensive training of four mixed operation sequences
comprehensive training is concive to the improvement of judgment ability, reaction speed and the consolidation of oral arithmetic
of course, we need to persevere in the above situations. Otherwise, it is difficult to achieve the expected effect if we fish for three days and dry the net for two days
the above five kinds of training should be carried out step by step, but also persevere. It will take some time to improve your math scores. Don't be too eager to succeed.
different age of primary school students, the basic requirements of oral arithmetic are also different. Low and middle grade students mainly add one or two digits. It is better for senior students to take the one digit by two digit mental arithmetic as the basic training. The specific requirement of oral arithmetic is to multiply the number of one digit and the number of ten digits of two digits, and then add the proct of multiplying the number of one digit and the number of one digit of two digits to the three digits, and quickly say the result. This mental arithmetic training includes the practice of several spatial concepts, digital comparison and memory training. In primary school, it can be said that it is a sublimation training of abstract thinking of numbers. It is very beneficial to promote the development of people's thinking and intelligence. You can arrange this exercise in two periods. One is to read early, the other is to arrange a group after homework. Each group is divided as follows: one digit is optional, corresponding to the number of one digit or ten digit in two digits. There are 18 questions in each group. Write the formula first, then write the number directly after several times of oral calculation. After a period of time, you will find that your speed and accuracy will be greatly improved< 2. Targeted training
the main form of the number of senior grades in primary school has changed from integer to score. In the number of operations, I believe we do not like the different denominator fractional addition, right? Because it's too error prone. Now, please think for yourself, is the addition (subtraction) method of different denominators only in the following three cases
1. For two fractions, the large number in the denominator is the multiple of the decimal
for example, "1 / 12 + 1 / 3", in this case, oral arithmetic is relatively easy. The method is: the big denominator is the common denominator of two denominators. As long as the small denominator is expanded by multiple, until it is the same as the big number, the denominator is expanded by several times, and the numerator is also expanded by the same multiple, It can be calculated by adding the same denominator fraction: 1 / 12 + 1 / 3 = 1 / 12 + 4 / 12 = 5 / 12
2. The denominator of two fractions is coprime
this kind of situation is more difficult in form, and I believe you are also the most headache, but it can be changed into easy: after it is divided, the common denominator is the proct of the two denominators, and the numerator is the sum of the proct of the numerator of each fraction and the other denominator (if it is subtraction, it is the difference of the two procts), such as 2 / 7 + 3 / 13. The oral calculation process is: the common denominator is 7 × 13 = 91, molecule 26 (2 × 13)＋21(7 × 3) = 47, the result is 47 / 91
if the molecules of both fractions are 1, the oral calculation is faster. For example, "1 / 7 + 1 / 9", the denominator is the proct of two denominators (63), and the numerator is the sum of two denominators (16)
3. Two fractions and two denominators are neither coprime numbers nor multiples of decimals
in this case, we usually use the short division method to get the common denominator. In fact, we can also directly calculate the general score in the formula and get the result quickly. The common denominator can be obtained by enlarging the large number in the denominator. The specific method is: to double the large denominator (large number) until it is a multiple of another denominator decimal. For example, 1 / 8 + 3 / 10 expands the large number 10, 2 times, 3 times and 4 times, and compares it with the decimal 8 every time to see if it is a multiple of 8. When it is expanded to 4 times, it is a multiple of 8 (5 times), then the common denominator is 40, and the numerator is expanded by the corresponding multiple and then added (5 + 12 = 17), and the number is 17 / 40
after reading the above, have you found the rule of mental arithmetic in every situation? So as long as you practice more and master it, the problem will be solved< (3) memory training
do senior students feel that sometimes the calculation content in the topic is very extensive? Some of these operations have no specific rules of oral arithmetic, so I have to solve them through memory training. The main contents are as follows:
1
2. The proct of the approximate value of PI 3.14 with one digit and with several common numbers 12, 15, 16 and 25
3. The denominator is the decimal value of the simplest fraction of 2, 4, 5, 8, 10, 16, 20 and 25, that is, the interaction between these fractions and decimals
the results of the above numbers, whether in daily work or in real life, are used very frequently. After mastering and remembering them, they can be transformed into abilities and proce high efficiency in calculation< 4. Regular training
1. Mastering the law of operation. There are mainly five laws in this aspect: commutative law and associative law of addition; Commutative law, associative law and distributive law of multiplication. Among them, the multiplication distribution law is widely used and has many forms, including positive use and negative use, and the forms of integer, decimal and fraction. In the multiplication of fractions and integers, we often ignore the application of the law of distribution of multiplication, which makes the calculation complicated. Such as 2000 / 16 × 8. If we use the law of multiplicative distribution, we can calculate the result of 1000 by mouth directly. But if we use the general method of recing false fraction, it is time-consuming and easy to make mistakes. In addition, there are subtraction properties and quotient invariant properties< 2. Regular training. It is mainly the oral calculation method of the square result of the two digit number of 5
3. Master some special cases. For example, in fractional subtraction, if the numerator is not enough to be subtracted after general division, and the numerator subtracted is usually larger than the numerator subtracted by 1, 2, 3 and other smaller numbers, no matter how big the denominator is, it can be directly calculated orally. For example, the difference between 12 / 7 and 6 / 7 is only 1. The difference between 12 / 7 and 6 / 7 must be 1 less than the denominator. The result is 6 / 7 without calculation. Another example is: 194 / 99-97 / 99, if the difference between the numerator and denominator is 2, the difference between the numerator and denominator is 2, and the result is 97 / 99. When the subtracted molecule is larger than the subtracted molecule by 3, 4, 5 and other smaller numbers, the result can be quickly calculated orally. Another example is the mental calculation of the proct of any two digit number and 1.5, which is two digits plus half of it< 5. Comprehensive training
1
2< 3. Comprehensive training of four mixed operation sequences
comprehensive training is concive to the improvement of judgment ability, reaction speed and the consolidation of oral arithmetic
of course, we need to persevere in the above situations. Otherwise, it is difficult to achieve the expected effect if we fish for three days and dry the net for two days
the above five kinds of training should be carried out step by step, but also persevere. It will take some time to improve your math scores. Don't be too eager to succeed.
8. Compared with the old textbook, the amount of calculation practice in the new textbook has been greatly reced, and the difficulty has also been reced a lot. However, I feel that the students' computational ability has dropped a lot compared with the previous students, the computational ability is poor, the computational speed is slow, and the computational error rate is high! To this end, I think the following measures should be taken: first, adhere to the practice of oral arithmetic, often unremitting“ In order to cultivate students' computational ability, we should pay attention to the basic training of oral arithmetic, insist on regular practice, and graally achieve proficiency. " This is the requirement of mathematics curriculum standard. In my teaching, I organized teaching and training in a planned, step-by-step and purposeful way, such as listening to arithmetic, reading cards and oral arithmetic, reading questions and calculating silently, and repeatedly emphasized that the first is correct and then fast. 2、 Strengthen the basic knowledge and improve the ability of written calculation. In the teaching of calculation, oral calculation is the basis of written calculation, and written calculation is the key. Written calculation plays an extremely important role in primary school mathematics teaching. No matter how advanced the technology is in the future, the ability of written calculation is always a necessary ability for primary school students. 1. To enable students to understand the basic knowledge of mathematics and master skills is the primary condition for the formation of computing ability. Each calculation is based on the corresponding concepts, rules, properties, formulas and other basic knowledge. If students don't understand these basic knowledge correctly and master them thoroughly, they can't calculate. Only after students understand and master the relevant operation properties, laws and skills, can they apply these knowledge in specific calculation to seek simple and reasonable methods, improve the accuracy of calculation and speed up calculation. 2. Strengthening practice and skill training is the key to the formation of students' computing ability. For example, in the calculation of four items of scores, we often encounter the situation that some students' calculation rules are correct but the calculation results are wrong. The reason for the error lies in the basic skills such as approximate score, general score or mutualization; Another example is the division of decimals, especially when the divisor is a decimal. The mistake is that when the divisor becomes an integer, the divisor does not expand the same multiple at the same time, resulting in a wrong quotient. So we should strengthen the training of basic calculation skills in calculation practice. 3. Memorize common data, improve the calculation speed. In the four operations, if students memorize some commonly used data, it will not only help students to achieve the "correct and rapid" requirements, but also help students to better master the skills of calculation. For example: special data with sum and proct of whole hundred and thousand (for example: 75 + 25 = 100 + 25) × 4=100 125 × 8=1000 The proct of the approximate value of PI 3.14 with one digit and the proct with several common numbers 12, 15, 16, 25 and 36; The denominator is the decimal value of the simplest fraction of 2, 4, 5, 8, 10, 16, 20 and 25, that is, the interaction of these fractions and decimals. The results of the above numbers, whether in daily work or in real life, are used very frequently. After mastering and remembering them, they can be transformed into abilities and proce high efficiency in calculation. 3、 Carry out computing competition activities. For the boring calculation, students often deal with it casually after mastering the calculation method, resulting in more calculation errors. At this time, the proper development of some computing competition activities, often can better mobilize the students' learning initiative, improve the interest in computing, and achieve the purpose of improving the accuracy of computing. This semester, I plan to carry out two calculation competitions in the class, in order to improve the students' interest in calculation and improve the accuracy of calculation. After the competition, pay attention to sort out the students' mistakes, analyze and classify them, and then make targeted remedies, so as to clear the obstacles for improving the students' computing ability. 4、 We should encourage students to have a pleasant learning experience. Teachers should encourage students to make mistakes e to carelessness. In the usual homework correction, we should affirm its strengths, enhance self-confidence, put forward ardent hope, and urge it to correct its shortcomings.
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