Nine-year compulsory education textbook, new mathematics textbook, grade two, first semester (trial version) p30

Teaching objectives:

1, through the process of exploring the multiplication relationship of 2, 4 and 8, cultivate students' observation ability.

2, a preliminary understanding of the law that one factor is doubled, the other factor is halved, and the product remains unchanged.

3. Knowing the relationship between multiplication of 2, 4 and 8 can solve some practical problems by using the relationship between multiplication of 2, 4 and 8.

4. Stimulate students' interest in learning and experience the joy of success.

Teaching focus:

The relationship between the multiplication of 2, 4 and 8.

Teaching difficulties:

Solve practical problems with the multiplication relation of 2, 4 and 8.

Teaching material analysis:

In the textbook, students are required to spell the calculation bars into rectangles and observe the relationship between the bars of three colors. They initially thought that 2, 4 and 8 all had the same 0.8 and 16. Then, through the jumping rays of three small animals as the main line, they also found that 2, 4 and 8 all have the same 8 and 16, and summed up the multiplication relationship of 2, 4 and 8. Knowing 1 8 = 2 4 = 4 2, find the truth that one factor is doubled and the other factor is halved, so that students can learn the methods and significance of inquiry, acquire knowledge and develop their abilities through arithmetic operation and explanation.

Teaching process:

First, review old knowledge and introduce new lessons.

1, answer orally.

2×4= ? 5×4= ? 2×9= ? 8×6= ? 4×3= ? 3×8= ? 6×2= ? 4×7= ? 5×8= ? 9×8=

2. Guess is exciting.

Teacher: Some time ago, we learned the multiplication of 2, 4 and 8. Everyone can skillfully calculate the multiplication formula of 2, 4 and 8. Is the multiplication of 2, 4 and 8 related? If so, what is the relationship between them?

Students are free to guess.

3. reveal the topic.

Teacher: Is everyone's guess right? Today we will study together.

Blackboard: Multiplication of 2, 4 and 8.

Second, hands-on operation and independent perception.

1. Work at the same table and spell out a rectangle with a calculation bar in hand. Requirements: bottom yellow stripe, middle red stripe and top blue stripe.

Communication and display, how do you spell it?

Media demonstration

Thinking: So what's the relationship between Huang Honglan stripes?

Students communicate and teachers write on the blackboard.

1 8 yellow stripes =2 4 red stripes =4 2 blue stripes.

1 8=2 4=4 2 1×8=2×4=4×2.

Teacher: If the teacher puts two yellow bars with eight squares at the bottom, how to put them in the middle layer? What about upstairs? What is the relationship between them?

Students communicate and teachers write on the blackboard.

2 yellow stripes with 8 squares =4 red stripes with 4 squares =8 blue stripes with 2 squares.

Two eights = four fours = eight twos.

2×8=4×4=8×2 【 The relationship between 2, 4 and 8 is preliminarily perceived through the operation of calculating slices. ]

Third, explore independently and deepen understanding.

(1) 1. Record filling form

Teacher: Today, the little frog, the little rabbit and the little kangaroo are going to play happily on the beach. Frogs jump 2 squares at a time, rabbits jump 4 squares at a time and kangaroos jump 8 squares at a time. They want our children to tick √ on the table on page 30 of the book.

The way of recording. You are willing to help.

2, report communication, according to the student's report.

Put a √ on the form.

By observing this form, have you found anything? Talk about your findings with your deskmate.

Summary: It turns out that the frog jump data is the product of 2, and the rabbit jump data is the product of 4.

The product of the data that kangaroos jump to is 8 times the product.

[By recording the data of small animals' long jump, we can further understand the multiplication relationship of 2, 4 and 8. ]

(2) 1. Just now, some students found that some products in the multiplication of 2, 4 and 8 are the same. Then let's find out the same product and compare it. Who found more?

Show blackboard writing

1 8 = 24 = 4228 = 44 = 828 =1× 816 = 8× 28 = 2× 416 = 4× 48 = 4× 216. Is there any rule to observe the factor and product of these two formulas? (Group discussion. )

Summary: The product of multiplication of 2, 4 and 8 is the same because one factor is doubled and the other factor is halved, and the product remains unchanged. (blackboard writing)

Step 3: Think.

2, 4 and 8 are multiplied by the same product. Anything else? what do you think?

【 Find out the product of the second, fourth and eighth parts in the table, and guide the observation and analysis of the formula of the same product. The summary factor changes according to a certain law, and the product remains unchanged. Do you have the same product to arouse the thinking of a capable child again by asking questions?

Fourth, consolidate new knowledge.

1, the students are very clever and found this rule. The first and second lines of P30/3 in that book. Do these topics also conform to this law? Please fill it out and think about it. (Complete and report independently. )

Conclusion: In fact, when we do such a problem, we can not only use formulas to help, but also answer it through the newly discovered laws.

2. How many () ×2=()×4 can I fill in for discussion and exchange? Complete the third line on page 30 independently.

[If there is a multiplication formula like 12×2=6×4] 12×2, we haven't learned it, but we can know that the product is 24 through the law we found]

3.Show: 18 × 4 =？

We have not studied this topic either. Who can figure out a way to work out the result?

(9)×(8)=(72 )

Summary: We can use the law discovered today that one factor is doubled, the other factor is halved, and the product is unchanged to convert the formula that cannot be multiplied by the formula into the corresponding formula to calculate the product.

[Stimulate children's thinking sparks by asking questions, and let students turn unknown knowledge into learned knowledge. Let's have a match.

( 1)56=8×()=()×()=()×()

(2) How many multiplication formulas can be written with the product equal to 64?

Ask the students who write the most to talk about the thinking process.

Verb (abbreviation of verb) course summary

What did you buy today?