Example 2 and related exercises on page 54, Volume 2, Grade 2 textbook

Teaching purpose:

1. Through practical activities, let students understand the meaning of "one number is several times that of another number" and realize the relationship between quantities.

2. Make students experience the process of "how many times one number is another" and learn to solve simple practical problems by transformation.

3. Cultivate students' cooperative consciousness and improve their inquiry ability.

Teaching focus:

Make students experience the process of abstracting the quantitative relationship of "one number is several times of another number" from practical problems, and solve practical problems with multiplication formula and quotient skills.

Teaching difficulties:

Using analytical reasoning, the quantitative relationship of "how many times is one number another" is transformed into "the division meaning of several other numbers contained in one number".

Teaching AIDS: sticks, multimedia courseware.

Teaching process:

First, oral communication of mathematics

(1) Five-minute oral math training

Four 7s are (), and the formula is ().

Eight fives are (), and the formula is ().

Six times 7 is (), and the formula is ().

3 times of 6 is (), and the formula is (

There are () 4 in 24, and the formula is ().

There are () 9s in 45, and the formula is ().

(2) Teacher-student dialogue: If you meet a stranger, what can you do to get familiar with him quickly?

(3) The teacher asked a student to demonstrate that two strangers asked each other questions and sought the answers to the questions.

Teacher: In mathematics, we often meet unfamiliar knowledge. We can ask him questions and seek answers to questions, and unfamiliar knowledge will be as familiar as our friends. Do students have the confidence to make unfamiliar knowledge your familiar friend? Teachers depend on students' performance. )

Second, group cooperative learning

(1) courseware shows the theme map.

Default question 1: Have you ever seen an airplane? Have you ever made an airplane? Observe the theme map carefully

Question 2: What mathematical information can you collect from this picture?

Question 3: Based on this mathematical information, what mathematical questions can you ask? (Students ask questions and teachers and students answer them. )

The teacher leads the students to ask questions about time division. If the students can't figure it out, the teacher can ask a question whether a number is another number, and then let the students ask questions. )

Let me see question ①: How many times as many sticks does Xiao Li use as Xiao Hong?

②: How many times does Xiao Qiang use a stick than Xiaohong?

(3) Xiao Qiang used a stick several times as much as Xiao Li?

If students can ask two other questions according to the question (1), they should be praised and encouraged.

(2) cooperative learning:

Teacher's question: Who can help the teacher solve this problem? Let's fly a plane in groups of four students and compare it to see how many times it is. what do you think? Discuss in groups. (Courseware demonstration requirements) Teachers' patrol guidance.

(3) The team reports the results and the teacher evaluates them.

Solve the first problem:

According to the report, the teacher wrote on the blackboard:

Xiaohong 1 rack 5 pieces11111.

Xiaoli210111111.

Xiao Qiang 31511111165438.

The teacher explained: How many did Xiaohong use? How many did Xiaoli use? How many 5s are there in 10? 10, how many are there in five? Then we can say that finding 10 is a multiple of 5, that is, finding how many 5s are there in 10, and how to calculate how many 5s are there in 10? How to form?

Who can say it completely? (Guide the students to say: Find 10 is a multiple of 5, that is, find how many 5s are in 10, and calculate by division. )

Communicate with each other at the same table first, then report separately and share the listening and evaluation with the whole class.

Solve the second and third problems:

Question: Can you solve the second question? what do you think? Why do you want to calculate by division? (Students fully indicate that finding how many times 15 is five means finding how many fives there are in 15. Let the students understand that finding how many times one number is another can be transformed into the problem of "how many digits does a number have" and calculated by division. )

Can you clarify the third question? Can you calculate? (The teacher explained that we didn't learn 15÷ 10, so we don't need to calculate the result. )

Third, expand and extend.

(1) What if there are four planes? How many sticks were used? (20) How do I ask questions? How many times are the sticks used by four planes as Xiaohong's? ) how to solve it? what do you think? (20÷5=4, how many times one number is another is calculated by division), and the teachers write it on the blackboard.

(2) What if there are five planes? How many sticks were used? (25) How do I ask questions? How many times are the sticks used by five planes as Xiaohong's? ) how to solve it? what do you think? (25÷5=5, find how many times one number is another, and calculate by division).

The teacher writes on the blackboard according to the answers.

The teacher explained that there is no need to write multiples after these formulas, and multiples cannot be used as units.

Summary: Today, we learned how many times one number is another, that is, how many digits a number has, all of which are calculated by division.