Textbook: Examples on page 34 of the second volume of Mathematics of Jiangsu Education Press, and "Thinking and Doing" on page 35 and related supplementary exercises.

< 2 >, teaching objectives

1. Through concrete operation and reasonable reasoning, it is found that how much one number is more than another is calculated by subtraction.

You can solve practical problems in life by exploring. And in the process of solving problems, cultivate the interest in learning mathematics and the consciousness of mathematics application.

(3) Emphasis and difficulty in teaching.

Through intuitive placement, explore new methods to solve problems, list subtraction formulas, and find out the difference between two numbers.

(4) Teaching preparation

Several small prizes; Some slides; Multimedia courseware; 6 copies of "one-on-one" materials; 2 "Find a friend" pictures and corresponding test questions; 2 pieces of "Pulling Radish" and corresponding test questions; 2 "sending letters" and corresponding test questions.

teaching process

First, create a situation to stimulate interest.

Dialogue: the teacher led everyone to a small animal party today ... there are many small animals.

Can you help "Aunt Peacock" line up the small animals according to their types and numbers?

Second, group cooperation, to guide the inquiry.

1. Distribute comparative materials, and draw the following conclusions through students' postures: Give an example of a wall chart of 1.

Say: My little white rabbit and the little black rabbit played a game with more flowers. What information did you learn from the pictures? What questions can I ask?

1. Show leading questions, students discuss and answer questions.

(1) Through pendulum observation, guide students to get the same number of parts and redundant parts, and tell how to get the redundant five.

② Through observation, let the students realize that 13 removes 8 pieces, and the remaining 5 pieces are more red flowers than yellow flowers, which are calculated by subtraction.

How to put it another way: "There are more red flowers than yellow flowers"? How to calculate?

(4) Assuming "a lot of flowers", can we compare their quantity by "pendulum"? See if there is any other way.

⑤ Leading reasoning, it is clear that subtraction is used to find a number larger than a decimal or a number smaller than a large number, that is, a larger number-a smaller number.

(2) Example 2: Wall chart. This example is completely free for students to answer independently, because the above teaching links have enabled students to have the ability to answer this question. This is also the students' initial experience in using the conclusion to solve problems.

Third, guide students to evaluate each other, and teachers give relevant rewards.

Fourth, have a rest.

Talk: The students did well just now, and the teacher was very happy. Now, will you give each group a small gift?

Play the music "Happy Birds" and let teachers and students do the "rhythm" together.

Fifth, consolidate practice.

Talk: Take a break and let's accept new challenges together!

↓ 1↓ game: break through three levels, the first level: find friends.

1, looking for friends. Find a friend. Figure 3 and corresponding problems. Let three students find the corresponding answers according to the questions in the music, that is, find a friend. At the same time, different rewards are given according to the situation.

& lt The white rabbit and the bear gather mushrooms together. The white rabbit picked 49= ""The bear picked 20. How many more white rabbits have been picked than bears? & ltP b, the white rabbit and the bear picked mushrooms together, and the white rabbit picked 49 mushrooms.

Dialogue: We all passed the first level successfully, which is worth celebrating! Listen to this friend: Little Rabbit whispered a few words to me. You want to know what it is? Xiao Mianzi told me that his radish garden had a bumper harvest, and he asked us to help him pull out carrots. Would you like to? The second level: pulling radish.

2, pull radish. Figure 3 and the corresponding test questions. Students pull out the corresponding radish according to the test questions. 〉

A, the little animals helped the little rabbit pull out radishes, and the little bear pulled out 30.

35 elephants were pulled out. How many more elephants are pulled out than bears?

B, the little animals helped the little rabbit pull out radishes, and the little bear pulled out 30.

The elephant pulled 35, how much did the bear pull less than the elephant?

C. The little animals helped the little rabbit pull out radishes, and the little bear pulled out 30.

Elephants pulled out 35. How much did they pull out?

Talk: Congratulations on successfully passing the second level again! Do you know why the rabbit's radish garden can get such a bumper harvest?

② The story "Ant and Guo Guo".

1, the big screen shows that students listen to the teacher while watching the pictures.

Little ants can spend the winter comfortably in the cave in winter because of their hard work; Fruit is cold, hungry and dying in winter because of laziness. Seeing the poor appearance of the fruit, the little ant generously gave some of his food to the fruit. So, with the help of ants, Guoguo passed the winter safely. How time flies! Another summer has arrived. Guoguo learned the previous lesson and prepared some food with ants in advance to prepare for the winter. Look, how well they are prepared: 54 grains of wheat, 40 grains of millet and 30 grains of soybeans.

2. Guide students to ask questions and answer them. How much more wheat is than millet? How much is soybean less than wheat? How much wheat and millet are there? How many wheat, millet and soybeans are there? Equal to >

3. Ideological education.

Talk: What do you think when students hear this story and see these things? Only by hard work can we get endless things; Only by working hard can we learn well; Only by bravely correcting mistakes can we make continuous progress. 〉

Sixth, summarize the evaluation and learn to use it.

Dialogue: What skills have we learned today, children? Can you compare the two quantities with the actual situation? The deskmates communicate with each other. What method will you use to solve the problem of comparing two quantities? Do you have any other good ways to tell your classmates?

Seven, contact with reality, solve the problem.