1, two scenes of multimedia demonstration.

(1) Passengers get on and off in disorder. Ask the students to comment on this behavior and guess the increase or decrease of the number of people on the bus. (uncertain)

(2) Passengers get on and off in an orderly manner (2 people get off and 3 people get on). Ask the students to discuss and think about how many people are on the bus. Guess how many people are in the car?

2. Narrator: Students, in order to find out the number of people getting on and off each time and the number of people on the bus, we should not only carefully observe the number of people getting on and off each time, but also add and subtract according to the original number of people getting on and off.

Second, actively explore and understand.

1, ask questions.

Multimedia demonstration cartoon: there are 7 people in the car, 2 people get off first, and then 3 people.

Question: (1) What did you see from the cartoon just now? Talk about it in the group. (2) Can you use school tools to show the riding situation just now? (3) Can you use an expression to express the meaning of a cartoon? (7-2+3=□)

2. Reveal the topic.

Question: What is the difference between this question and the addition and subtraction we have learned?

3. Explore the algorithm.

Question: How to calculate the formula of addition and subtraction? Students think independently.

Blackboard: 7-2+3=8

Let the students talk about the calculation process together: first calculate 7-2=5, then 5+3=8, so 7-2+3=8.

Third, consolidate and deepen, apply and expand.

1, multimedia shows a beautiful forest animation.

Guide students to look at the pictures and say what they mean.

Students describe in groups and fill in the blanks.

Find some classmates to talk about the calculation process, then communicate with each other at the same table, and then communicate with the whole class together.

2. Multimedia demonstration: The giant panda happily leads everyone forward across the field. In front of us is a lawn with rockeries and pavilions, which leads to the second question "Thinking and Doing".

Students exchange pictures and ideas in groups and fill in the blanks.

After finishing, check each other in the group, count the number of people who do it right, and correct the mistakes.

3. Multimedia demonstration: Through the grass, bypassing the pond, everyone came to the forest, and the fifth question "Think and do" appeared.

Dialogue: There are monkeys, pandas and rabbits in the big forest. What kind of formula do you want to make? Please fill in the blanks in the group. After filling it out, say the meaning of each formula in the fence first, and then communicate with the class.

4. Question: The white rabbit is tired of jumping over the fence. Shall we help him pick loofah?

Multimedia presentation "Thinking and Action" Question 4. Students contact and communicate with each other.

Fourth, class summary.

Multimedia continues to demonstrate: The giant panda said, "The children did very well today. In fact, it's not just the big forest that has math knowledge. As long as the children pay attention, you are surrounded by math knowledge. I hope you study hard and welcome you to the big forest again. Goodbye, children! "