1. Make students master the conversion method of percentage and decimal, and make it correct.

2. In the process of mutual learning, make students realize the internal relationship between them, and lay a foundation for the calculation and application of learning percentage in the future.

3. Cultivate students' analytical thinking and abstract generalization ability in the learning process.

Emphasis and difficulty in teaching

Make students understand the method of mastering the reciprocity of percentages and decimals.

teaching tool

courseware

teaching process

First, the activity (1) review preparation

1, the courseware displays the review questions.

The number of times that Zhang Yu skips rope is 1.37 times that of Chen Cong.

The number of skipping rope in Wang Zhixiang is 6/5 of that in Chen Cong.

The number of skipping ropes in Liu Xingyu is 137.5% of that in Chen Cong.

Thinking: Who jumps the most of these three people? How do you compare them?

2. Introduce new courses.

In production, work and life, in order to facilitate statistics and comparison, we often use percentages to represent some data. What figures can you use besides percentages?

In this lesson, we will learn the conversion between percentages and decimals and the conversion between percentages and fractions.

Second, the activity (2) the reciprocity of percentages and decimals.

(1) The process of recalling fractional decimals.

(2) What should be the denominator when converting decimals into percentages? How to make its denominator 100?

Three. Activity (3) Decimal percentage

1, for example 1: convert 0.25,1.4,0.123 into percentages.

How many steps are there in (1) decimal percentage?

② Students answered, and the teacher wrote on the blackboard: 0.25=25/ 100=25%.

③ 1.4 How to divide a component into fractions with the mother of 100? According to what?

④? Do it. Convert the following decimals into percentages.

0.38 1.05 0.055 3

⑤ What happened after the decimal of observation example 1 was converted into percentage?

Do you have the same change in the number of exercises you do? What does this change conform to?

Now can you quickly convert the following decimals into percentages? (oral answer)

2.5 0.785 0. 16

2. Example 2: Decimal 27%, 135% and 0.4%.

Students try to do it by themselves, and students summarize the methods.

(1) Talk about the method of percentage decimal.

② Observe what happens when percentages are converted into decimals?

③ Extract the following percentage.

15% 80% 3.5%

3. summary.

Through the analysis and induction just now, who can tell us how percentages and decimals interact?

Fourth, consolidate and improve.

1、P80？ Do it.

Exercise 2 of19.

Verb (short for verb) homework

Exercise 19, question 1

homework

Exercise 19, question 1

"Conversion of Percent, Fraction and Decimal" Teaching Plan (2) Teaching Objectives

1, so that students can understand and master the method of conversion between percentages and decimals, and can correctly convert fractions and decimals into percentages or components.

2. Cultivate students' abstract generalization ability in the process of calculating, comparing, analyzing and exploring the mutual transformation law of percentage, fraction and decimal.

3. Stimulate students' consciousness of mathematical exploration by exploring the mutual transformation law of percentage, fraction and decimal.

Emphasis and difficulty in teaching

Teaching emphasis: master the method of conversion between percentage, fraction and decimal.

Teaching difficulties: correctly and skillfully convert percentages, fractions and decimals.

teaching process

First, review.

Students, what is a percentage? The students answered.

1, fill in the blanks

The number of boys accounts for 5 1% of the class, that is to say, () is regarded as 100, () accounts for 5 1% of the class, and the number of girls accounts for ()% of the class.

2. Decimalize the following into components, and explain how to realize it.

0.45 1.20.367

3. Tell me how to do the fraction below the decimal.

1/2 2/5 4/ 10 2/ 100

4. Write down the following percentages.

Sixteen percent, 72.500 percent, 180 percent and 500 percent.

5. What is the number 100 times? How does the decimal point move? What if it is reduced by 100 times? How does the decimal point move?

2.55 0.48 1.25 10.3

Second, new funding.

1. Teaching examples 1.

(1) Give an example of 1: convert 0.25,1.4,0.123 into percentages.

(2) Guide students to think: To convert decimals into percentages, first convert decimals into fractions with 100 as the mother, and then rewrite this fraction into percentages.

Complete independently, refer to the performance of the board.

0.25=25/ 100 =25%

1.4= 14/ 10= 140/ 100= 140%

0. 123= 123/ 1000= 12.3/ 100= 12.3%

(3) Formula of the blackboard: Please follow it. What did you find? Acoustic discussion. Of the discovery of life.

Summary:

If you don't look at the process of component priority, how can decimals be directly converted into percentages?

(Guide students to summarize the method of converting decimals into percentages: To convert decimals into percentages, just move the decimal point two places to the right, followed by hundreds of semicolons. )

To convert decimals into percentages, just move the decimal point two places to the right and add hundreds of semicolons at the end.

(4) Description: If the decimal point is moved to the right by two places, the original number will be expanded by 100 times, and if hundreds of semicolons are added, it will be reduced by 100 times. So the size of the original number is constant.

(5) Exercise: Turn the following decimals into percentages.

0.07= 0. 125=

2. 1= 6.6=

4.076= 0. 108=

2. Teaching Example 2

(1) Example 2:

Draw the following percentage.

27% 135%

(2) Guide students to think: To convert percentages into decimals, you can first rewrite the percentages into fractions with the initial letter 100, and then divide the numerator by the denominator to convert the fractions into decimals.

(3) inspire students to dictate the transformation process of each question,

Blackboard writing:

27%=27/ 100=27? 100=0.27

135%= 135/ 100= 135? 100= 1.35

(4) Guide students to observe and summarize. How to quickly and directly convert percentages into decimals?

To convert percentages to decimals, simply remove the percent sign and move the decimal point two places to the left.

(5) Let students understand that if the percent sign is removed, the original number will be expanded by 100 times; Then move its decimal point two places to the left, reducing it by 100 times, and the size of the original number remains unchanged.

(6) Finish page 80? Do it. Question (2), (presented on the blackboard)

3. Summary: Guide students to further comprehensively summarize the methods of percentage and decimal exchange: to change decimals into percentages, just move the decimal point to the right by two places, followed by hundreds of semicolons; To convert percentages to decimals, simply remove the percent sign and move the decimal point two places to the left.

4. Teaching Example 3

Example 3:

Qingyang primary school grade six class one physical education Committee member

The investigation is complete, I can swim, I can.

After counting the number of skaters, the following results are obtained.

Will you use percentage to express the above scores?

(1) Students discuss in groups and find out how to convert scores into percentages.

(2) Group report and write it on the blackboard.

(3) According to the students' answers,

Blackboard: 3/5 =3? 5=0.6= 60% 3/5=60/ 100=60%

2/7=2? 7=0.2857=28.57%

Convert 1/6 to a percentage.

(the numerator is divided by the denominator, and three decimal places are reserved when it is inexhaustible, that is, one decimal place is reserved before the percent sign. )

Example 4: Divide the following percentages into several parts.

50% 45% 67% 37.5%

(1) Students find out how to divide percentages into components through group discussion.

(2) Guide students: Percent is a part of the score and can be written in the form of a score. Please use what you have learned in the past to try to rewrite the above scores into percentages.

(3) According to the students' answers,

Blackboard: 50% = 50/100 =1/245% 45/100 = 9/20.

67%=67/ 100 37.5%=37.5/ 100=375/ 1000=3/8

(4) Think about it: How to divide the 2.5%? (If the numerator of the percentage is a decimal, the numerator and denominator can be enlarged by the same multiple at the same time according to the basic properties of the fraction, so that the numerator becomes an integer, and then the fraction can be simplified. )

(5) In ○.

Third, consolidate the practice.

1, arrange the following numbers (from largest to smallest).

2. Fill in the blanks.

3. Judges:

( 1).0.6%=0.6 ( )

(2) After .30, add? %? The obtained number is 100 times larger than the original number. ( )

(3). 15.5% magnification 10 times is 155. ( )

(4) To convert decimals into percentages, just move the decimal point two places to the right, followed by hundreds of semicolons. ( )

4. Thinking: Take out a rectangular or square piece of paper, fold it in half for three times, and then express one of them as a fraction (), a percentage as () and a decimal as ().

( )

There are 25% more cows than sheep, and sheep

How many percent is the head count less than that of cattle?

5/8 of the weight of apples is 4/5 of the weight of pears.

(1). The weight of apples is 80% of that of pears.

The weight of pears is ()% of that of apples.

(3). Pears are lighter than apples ()%

(4) Apples are 80% heavier than pears.

100 increases 10% decreases.

Subtracting 10% is ().

The price of a schoolbag is 25% lower than last year and 20% lower than the previous year. How much is the price this year lower than that of the previous year?

Fourth, homework

Exercise 19, questions 5, 6 and 8.