Teaching objectives

1. Knowledge and skills:

(1) Let students understand the meaning of the approximate value of quotient.

(2) Mastering the method of "four houses and five people" to get the approximate value of quotient, we can get the approximate value of quotient correctly according to the meaning of the question.

2. Process and method: approximate values can be obtained according to actual conditions.

3. Emotion, attitude and values: cultivate students' mathematical knowledge and the ability to use it flexibly in real life.

teaching process

First, review.

1, oral calculation.

0.63÷7 0.24÷0.3 0.65÷0. 13

72÷ 144 1.44÷0.6 5.6÷0.08

2. Calculate the approximate value of the following decimals according to the method of "four houses and five people".

3, column vertical calculation.

24.723÷6.7 20.88÷0.58

Question: How to calculate the division with decimal divisor?

4. The teacher pointed out that this lesson will learn the application of decimal approximation in division.

Second, the new teaching

1, example 7 on page 23 of the textbook.

Exhibit 7: Dad bought a new tube of badminton for Wang Pengxin. How much is this tube of badminton 19.4 yuan 1?

Question: What is the badminton 1?

According to the known conditions and problems of the topic, make your own independent formulation. ( 19.4÷ 12)

In daily life, what is the smallest unit when we pay? (Angle or minute)

If it is an angle, how many decimal places should be reserved? (One decimal place)

If it is a fraction, how many decimal places should be reserved? (two decimal places)

Interpretation method 1:

19.6 ÷12 ≈1.6 (yuan)

The quotient of "four hospitals and five people method"

Teacher: If you keep one decimal place, you just need to divide it by the second decimal place, and then according to

Method 2:

19.6 ÷12 ≈1.62 (yuan)

The quotient of "four hospitals and five people method"

Teacher: If you keep two decimal places, you only need to divide it by the third decimal place, and then according to

2. Summary: When calculating currency, it is usually calculated by "angle" or "minute", so it is enough to keep one or two decimal places in the calculation formula. In daily life, the quotient obtained by fractional division can also keep a certain number of decimal places as needed to get the approximate number of quotients.

3. Consolidation exercise: "Doing" on page 23 of the textbook

After the students finished independently, the teacher commented.

Summary: When calculating the fractional division, when the quotient of the divisor is needed, it is generally divided by one more decimal place than the decimal place to be retained, and then one digit is removed by rounding.

Third, homework

1. Class assignment: Exercise 4 on page 26 of the textbook 10- 13.

2, expand the practice

(1) Calculate the following problem (keep one decimal place)

14.36÷2.7 8.33÷6.2 1.7÷0.03

(2) Calculate the following problem (the quotient is accurate to one percent)

32÷42 1.25÷ 1.2 2.4 1÷0.7

(3) Calculate the following question (the number is reserved to the percentile)

5.63÷6. 1 4.2÷4.5 2.84×0.03 6.64÷3.3 0.382×0. 13 38.2÷2.7