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How to solve the problem of wide-angle pancakes in the first volume of mathematics in the fourth grade of primary school
Teaching preparation courseware, paper pot, colorful circular pictures, tables, exercise papers.

teaching process

First, create situations and introduce new lessons.

1.Teacher asks: In daily life, we often encounter some math problems, such as: it takes 8 minutes to cook an egg, and how long does it take to cook 5 eggs?

Generate 1 by default: cook one by one, one for 8 minutes, and five for 40 minutes.

Default Generation 2: Put 5 eggs into the pot and cook them together, which takes 8 minutes.

2. Ask again: Why do you think of cooking together?

3. Teacher's summary: When five eggs are put into the pot to cook together, it can save both time and energy. It seems that boiled eggs should pay attention to methods! There are still many such problems in life, so let's study one of them-the "pancake problem" which also needs to pay attention to methods. Writing on the blackboard: pancake problem.

Design intention: create a life-like teaching situation to stimulate students' interest in learning. At the beginning of this class, I started from the simple case of "boiling eggs" in my life, mobilized the students' existing life experience, and guided the students to review how to arrange the operation reasonably at ordinary times to save time, so as to prepare for the infiltration of optimization ideas in new knowledge teaching.

Second, explore independently and explore the branding method.

(1) Interpret the information and understand the pancake rules.

1.Courseware presents the theme map. Guide students to observe and find the key mathematical information: you can only bake two cakes at a time, both sides should be baked, and each side takes 3 minutes.

2. Teachers ask questions, guide students to think, and let students deeply interpret mathematical information:

(1) What do you mean you can only bake two cakes at a time? (Guide the students to understand that only two cakes can be baked at a time, which means that at most two cakes can be put down in the pot at the same time. If there is only one cake, you can also put only one. )

(2) Do you want to brand both sides? A cake should be branded on the front and the back. ) The teacher stressed: For the convenience of expression, we can call the first branded side positive and the second branded side negative.