The teaching content of the second volume of the fourth grade mathematics, Comparison of Decimals (1);
Comparison of decimal sizes
Teaching objectives:
1, so that students can master the method of comparing decimal sizes according to the bit value principle of numbers, compare decimal sizes, and arrange more than two decimals according to their sizes.
2. By comparing the sizes of decimals, we can penetrate the idea of comparison and initially realize that big and small are relative.
Teaching emphasis and difficulty: find out the method of comparing decimal size and solve practical problems.
Teaching process:
First, create a situation
1. The teacher went out to buy some school supplies for his nephew on Sunday. When he saw many school supplies in the supermarket, he couldn't decide what to buy. Please ask the teacher for help to give advice today. Would you like to?
2. Show courseware: The teacher excerpted some articles he wanted to buy. What do you want to say when you see this?
Courseware display: yellow schoolbag, red schoolbag calculator, pen, ballpoint pen, pencil case.
28.5 yuan 28, 45 yuan 13, 38 yuan 13, 5 yuan 7, 25 yuan 13 and 8 yuan.
Second, study the method of decimal size.
1. If I choose between a yellow schoolbag and a pencil case, what do you think I should choose? Tell me your reasons.
If I choose between a pencil case and a ballpoint pen, what do you think I should choose? Tell me your reasons.
If I want to buy him a pen, what do you think I should choose? Tell me your reasons.
If I want to buy a schoolbag, what do you think I should choose? Tell me your reasons.
If I choose between a calculator and a pencil case, what do you think I should choose? Tell me your reasons.
2, you also said a few similar ones.
3. Too many. Can you sort out the comparison above and how to classify it properly?
Discuss the classification methods in groups and give feedback.
4. According to the classification, we can get the scheme of decimal comparison.
(1) If the integer parts are different, how to compare them? (Show Scheme I after discussion)
Courseware presentation scheme 1: look at their integer parts first, and the bigger the integer part, the bigger the number.
(2) If the integer parts are the same, how to compare them? Ten people are the same? (After discussion, Scheme 2 and Scheme 3 will be put forward.)
Courseware presentation scheme 2: When the integer parts are the same, look at the decimal places, and the number with the largest number on the decimal places will be the largest.
Option 3: When the deciles are the same, the higher the percentile, the higher the percentile. Analogy in turn
Step 5 give it a try
Example 5: Compare the sizes of 6, 35 yuan and 6,41yuan. Tell me how do you compare? (How to show the proportion of courseware)
Example 6: Compare the dimensions of 0,08m and 0,069m. And tell your deskmate what you think.
Third, application
1, fill in () >; , & ltOr =, and feedback.
2、54( )2、 14 0、746( )0、764 3、79( )3、79
2. Courseware should show size and gestures.
0,8 and 0,790,36 and 2, 1 1, 92 and 1, 092 2 and 2,9999 0,98 and 1.
0.67 and 0.760489 and 0.56060 and 6,065,60 and 5,600.
3. Application courseware demonstration: In the school sports meeting, the top four high jumpers are: Zhang Hua 1, 1m, Li Jie 1, 2 1m, Wang Xin 1, 2m, Chen Xiao 1, 000. Arrange them from high to low.
After reading the questions, think about their sizes, and then compare the sizes on behalf of everyone in groups.
4. Arrange the following figures in descending order.
4、45 5、4 4、5 4、445
Arrange the following figures in descending order.
0、6 0、6 1 0、60 1 0、6 1 1
Fourth, summary.
What skills have we learned today? Help the teacher decide what to buy with the newly learned skills.
Fifth, improve the problem after class: (find a friend to solve it together. )
The heights of a, b, c and d are 1, 46m, 1, 52m, 1, 38m, 1 and 5m respectively. As we all know, A is shorter than the referee, but shorter than C, D is shorter than B and A is higher than B ... Do you know the beat of A, B, C and D?
The teaching plan of the second volume of the fourth grade mathematics "Comparison of Decimals" (2) Teaching objectives;
1, familiar with the methods and steps of comparing decimal sizes, able to arrange the sizes of several numbers according to requirements.
2. By comparing the size of decimals, deepen students' understanding of the meaning of decimals.
3. Cultivate students' observation ability and judgment ability.
4. Let students experience the fun of learning mathematics in communication and cooperation.
Teaching focus:
Will compare the sizes of decimals.
Teaching difficulties:
Mobilize students' existing knowledge and experience and promote the transfer of knowledge.
Teaching preparation: courseware
First, the blackboard writing topic
(blackboard title: comparison of decimal sizes)
Second, explore new knowledge.
Now please open your books and turn to page 60. Let's look at this picture in the book. What are the children doing in this picture? What information can you get from this picture?
Health: They are in the long jump, Xiao Ming. ...
Teacher: There is a table next to the picture, which records their long jump scores. Let's look at their scores. (Stick a card)
Teacher: There is a question under the grade. Who will look at this question?
Health:
Teacher: What's the ranking?
Health:
Teacher: Then let's help them rank together! We will rank these four students before and after. It is necessary to compare their achievements one by one. Then the teacher divided them into two groups and compared them to see who would win.
Teacher: The teacher first divided them into two groups, Xiaoming and Xiaohong, Xiaoli and Xiaojun. Let's take a look at Xiao Ming and Xiao Hong's grades first. How should these two grades be compared? Any child wants to talk about his ideas.
Health: Xiaoming and Xiaohong are bigger than Fang, 3 to 2, so Xiaoming jumps farther than Xiaohong.
Teacher: (Summary) The ratio of Xiaoming to Xiaohong is 3,05 and 2,84, where 3 and 2 are their integer parts, and 3 is greater than 2, which is the integer part of these two numbers. The larger the integer part, the larger the number. Then when children want to compare two decimals, they must first compare the integer part. (blackboard writing: compare the integer parts first)
Teacher: Let's take a closer look at the scores of these students. Only Xiao Ming's score is above 3 meters, so we can say that Xiao Ming jumps farthest. If you give him a ranking, he will be the first.
Teacher: Next, let's compare the scores of Xiao Li and Xiao Jun. In their scores, the integer part is 2. So, how should we compare?
Student: Compared with the next one, Teacher: The next one is ten.
Teacher: We need to compare the scores of 8 and 9, which is bigger, 9, which means Xiaojun's score is bigger than Xiaoli's. Let's take a look at Xiaohong's score. The score of 2,84 meters and 10 is also 8, so Xiaojun jumps farther than Xiaohong. If you give Xiaojun a ranking, where should he rank? (2)
Teacher: Now only Xiaohong and Xiaoli have not come out. Who is the third place?
Health: Xiao Li.
Teacher: Oh, why do you think it's Xiao Li? Tell me your reasons.
Health: Because when comparing 2,88 with 2,84, the integer part and the tenth number are the same, so it is better than the next one.
Teacher: The next one is the percentile.
Health: The percentiles are 8 and 4, and the percentile is 8 or 4, so Xiaoli jumps further.
Teacher: Do you agree with this statement? Who else wants to talk?
Health:
Teacher: So Xiao Li is the third and Xiao Hong is the fourth.
Teacher: Now let's look at their rankings. What symbols can be used to connect them?
Health: greater than numbers
Teacher: It's really good. When we compared the scores of several of their classmates just now, we actually compared several decimals. Who can tell us how to compare the sizes of decimals?
Health:
Teacher: When comparing decimals, compare the integer parts first. If the integer parts are the same, compare decimals. When the deciles are the same, compare the percentiles.
Teacher: What if we can't compare sizes with percentiles?
Health: one in a thousand.
Teacher: You have to compare one by one until you can compare the sizes.
Third, expand applications.
Teacher: Now that the children have understood how decimals are compared in size, please turn to page 60 and fill in some data and symbols in the examples first. When you are finished, please watch and do it, and see which child can quickly compare the sizes of these groups.
(1)3 yuan () 2, 6 yuan
Teacher: How do you compare? Health: The integer part 3 is greater than 2.
(2)6.35 meters () 6.53 meters
Teacher: Who are you competing with? Health: Ten places.
(3)4、723()4、79
Teacher: 4732 is four digits and 479 is three digits. How can four digits be smaller than three digits?
Health: in percentile, 2 is less than 9, so 4,79 >; 4、723
Teacher: Oh, that is to say, when the decimal number is large, you can't count it in digits, or the number with more digits is large, which is also the difference from integer.
(4)0、458()0、54
Teacher: Do the children have anything to say when they do a few questions?
Health: I know the difference between integer size and fractional comparison size.
Teacher: What's the difference between them?
Health:
Teacher: Remember, children, when comparing decimal sizes, you should not look at the digits, but start with the integer part, and then go from decimal to percentile, from high to low.
Fourth, practice consolidation.
Teacher: Next, let's look at these small questions on the blackboard and tell us from whom you compared their sizes.
6、4( )5、9 12、4( ) 13、08 3、2 1( )3、 12
4、83( )4、59 4、36( )4、37 12、352( ) 12、36
Teacher: The students are very good. They can quickly and accurately compare which number is bigger and which number is smaller. The teacher wants to ask, what did you learn in this class today?
Health:
Teacher: The students have learned a lot. Then when you go home, use what you have learned today to complete questions 5, 6 and 7 of exercise 10 on page 65.
Five, the blackboard design
leave out