Teaching objectives:

1, combined with the familiar life situation and existing life experience, preliminarily understand the significance of subtraction. Learn to ask subtraction questions and answer them from specific situations.

2. Explore the subtraction of numbers within 5 in the activities of independent thinking, hands-on operation and cooperation and communication with peers.

3. Initially cultivate the ability to express one's own thinking process in an orderly manner, listen carefully and understand other people's ideas, and experience the fun of using mathematics.

Teaching emphasis: can correctly calculate the subtraction within 5.

Teaching difficulty: understanding the significance of subtraction.

Teaching process:

Talk before class: Grandpa Wisdom asked Mr. Wang to bring five wisdom stars. Look, he said, he will send these five stars of wisdom to our class 1 (8) for a meeting, so that smart children can listen, observe, talk and concentrate. Want these stars of wisdom? Look at everyone's performance!

First, create feelings and introduce new courses.

Xiaoxiao's apples are ripe. She invited us to her home. Do you want to go?

Second, explore the operation and understand the meaning

(1) How many apples are left?

1. Look carefully. How many apples are there on this apple tree? What happened now? How many apples have dropped? How many apples are left on the tree now?

Can you tell the math story completely?

There used to be five apples on the tree, but two were dropped and three were left on the tree. )

2. Can you express two mathematical information completely and put forward a mathematical problem according to this mathematical story?

There are five apples, but two have dropped. How many apples are left? )

3. How many books are left on the blackboard?

Today we will solve the remaining math problem.

4, put a pendulum.

Teacher: We just told this math story. In fact, we can put it out with school tools. Please take out five discs instead of five apples and put them away.

The students began to swing a pendulum. (Put five wafers first, take two wafers, and three more)

5. What can I say? How do you know there are three apples left?

Lead the students to say: If you remove two from the five totals, you will lose two and leave three.

6. Blackboard mapping.

Emphasis: If you remove one part from the whole, the rest is another part.

(2) How many pieces of cheese are left?

1, count it, a * * *, how many pieces of cheese are there? Look, what is the little mouse doing?

Can you tell the math story completely?

(There are 5 pieces of cheese, 2 pieces to be removed, and 3 pieces left)

2. Can you express two mathematical information completely and put forward a mathematical problem according to this mathematical story?

There are five pieces of cheese, how many pieces are left after removing two pieces? )

3, put a pendulum. Talk to each other at the same table

Can you put the meaning in the picture on a CD? Tell each other at the same table how you set it up.

4. Blackboard mapping.

Emphasis: If you remove one part from the whole, the rest is another part.

5. Draw a picture.

Can you draw the process just now?

Teacher's guidance: Math stories can be told, played and drawn. We can use figures (such as circles, triangles, squares, etc. ) instead of cheese, how to draw five pieces of cheese, take two pieces, think about it and draw this process in our book.

6. Exchange of reports.

Teachers guide the combination of expression and operation, shape and number, and realize the significance of subtraction.

Third, abstract understanding, cognitive subtraction

1. Who wants to tell these two math stories again?

2. Let's use an expression to express these two mathematical stories. How come?

Blackboard: 5-2 = 3

Do you know what each number stands for?

Let the students talk about the situation.

4. Know the minus sign and read the formula.

Here-it's a minus sign, which means get rid of it. An algorithm with a negative sign like this is called subtraction, supplementing the subject and understanding subtraction.

Teacher: How do you pronounce this formula? (5 minus 2 equals 3)

Reading from left to right, can you exchange the numbers on both sides of the minus sign?

5. Why do these two math problems need to be calculated by subtraction?

Inductive induction: after removing a part from the total, how much is left by subtraction?

There are many examples of subtraction calculation in our life. Let's take 5-2=3 for example. What mathematical story can it possibly tell?

Guide students to express themselves completely.

For example, five sweets, after eating two, there are three left. 5 yuan money, 2 yuan money, 3 yuan money.

Fourth, comprehensive exercises to deepen understanding

1, draw a picture, calculate.

Guide the students to look at the pictures, try to practice and report the communication.

2. Exercise 1 question.

First, let the students say the meaning of the picture, then list the formulas and report collectively.

Five, evaluation summary, expand the application

Comment on the wisdom star, and the teacher will give awards to the wisdom star brought by the wise old man. If you take 1 from these five, how do you want to record the process? The formula is 5- 1=4. What if I take two tablets at a time? 5-2=3

What if I take three at a time? 5-3=2

What if I take four at a time? 5-4= 1

What if I take five at a time? (Take it all away) 5-5=0 Next class, we will continue to learn the subtraction of the number 0.

Teacher: What did we learn today? What did you get? How do we know subtraction? What's the point of subtraction?

Attached book design:

How much is left (knowing subtraction)

Figure 1 Five apples dropped two and there were three left.

Figure 2 Five pieces of cheese. Take two, and there are three left.

5 - 2 = 3

minus sign

Reading: 5 minus 2 equals 3.