1. Introduce decimals.
Teacher: Students, the teacher went to the supermarket yesterday and found that everything had a price tag. Let's look at some excerpts from the teacher. (Show courseware)
Cold drinks 2.5 yuan Oreo cookies 12. 12 yuan.
Coke, 4.05 yuan? Yogurt, 2.60 yuan.
Teacher: Look at this set of numbers. Do they have anything in common?
Health: Everyone has a dot.
Teacher: Numbers with a dot in the middle like this are called decimals.
2. Reveal the topic.
Teacher: In this class, let's learn "Preliminary Understanding of Decimals" (blackboard writing topic).
3. Know the decimal point (to guide writing).
Teacher: We know that there is a straight line in the score, which is called the fractional line. Guess what the dot in the decimal is called?
Student: Decimal point
Teacher: Good guess. His name is a decimal point. (blackboard writing: decimal point)
Teacher: His home is in the lower left corner in the middle of the number.
Second, explore new knowledge.
(1) Decimal reading and writing
1. Read and write decimal.
Teacher: Now we know that these figures are decimals. The teacher has a new problem again. Students, can you read these decimals? Who will try to read the first decimal?
Health: refers to the decimal just read.
Teacher: Students, you only found it when you were reading decimals. Do the left and right sides of the decimal point sound the same?
Students' summary reading method: the left side of the decimal point is read according to the integer reading method we have learned, and the numbers on the right side of the decimal point are read one by one from left to right. Just like we read phone numbers.
(B) understand the practical significance of decimals
Decimal meaning of 1. element.
Teacher: Er, when did lazy sheep come to the supermarket? Seeing his blank face, he must have met with some difficulties. What can I do for him? Let's listen to his opinion.
Lazy sheep: I don't know how many yuan and cents these prices represent.
Teacher: Students! Do you know how many yuan cents these prices represent?
Health: refers to the quoted price.
Teacher: What does the one to the left of the decimal point mean? What does the first number to the right of the decimal point mean? What does the second digit to the right of the decimal point mean?
The students answered, and the teacher wrote on the blackboard: Jiao Yuanfen.
2) Show the commodity price list in the textbook, which students can complete independently.
Teacher: What kind of goods do you want to talk about?
Health: refers to the health report
Teacher: What do you mean by consolidating the decimal part again?
2) Look in your pencil box or on your desk, where there are decimals.
2. Explore how decimals represent length. (Understand the meaning of decimal parts in time)
Teacher: Students, now we know that we can use decimals to express prices. Can decimals represent other quantities? What else do you want to express in decimals?
Students: 1 students, 2 students, 3 students (students want to express something in decimals, and teachers should respond in time)
Teacher: Students, although it is called decimal, its function can be calculated. Let's discuss how decimals represent length.
Teacher: What unit of length do we know?
Health: centimeters? Decimeter? Mi …
Teacher: Students compare the length of 1 meter by hand. (Show courseware 1m)
1) Divide 1 meter into 10 parts, and each part is 1 decimeter.
1 decimeter =110 meter =0. 1 meter.
3 decimeter =3/ 10 meter =0.3 meter.
Teacher: 1 cm is longer?
2) 1cm = 1/ 100m = 0.0 1m。
3 cm =3/ 100 m =0.03 m
Teacher: The students did well. Now the teacher will make it a little harder to see if the students can still.
18cm = 18/ 100m = 0. 18m ..
Summary: Decimals with denominator of 10 can be written as one decimal, and decimals with denominator of 100 can be written as two decimal places.
Teacher: Say any centimeter or decimal. Student answers
Teacher: Are you going to test your deskmate? You can also say a centimeter and decimal casually, and the students at the same table will answer.
3) Use decimals to express height.
Teacher: The number of centimeters mentioned by the students just now is not more than one meter. Now the teacher has added a little difficulty. How to express more than one meter in decimals? Our height is over one meter.
4) When expressing the length, what is the number to the left of the decimal point? What does the first number on the right mean? What does second place mean?
(3) Practice and consolidate (show courseware)
Teacher: Now the teacher will test everyone to see if the students can skillfully use decimals.
1) do P89. (Students independently complete the collective revision of the report)
2) Complete the P90 question 1. (Students independently complete the collective revision of the report)
3) Read and write decimals by guessing riddles. (giraffe, African elephant, ostrich, red-crowned crane, Mount Everest)
4) I am a little teacher today.
Third, expand reading: "Do you know?" Cultivate students' pride in the motherland and understand the mystery of mathematics development.
Fourth, the class summary: talk about what we learned in this class.
Verb (short for verb) homework
Go home and measure the height of yourself and your family. Tell them how tall they are. How many meters are expressed in decimal.
Blackboard writing:
Jiao yuanfen? 1 decimeter =110m = 0.1m
1? 2? . ? 1? 2 yuan? Pronounced as:12:123m = 3/10m = 0.3m.
2? . ? 6? 0 yuan? 1cm = 1/ 100m = 0.0 1m
4? . ? 05 yuan 3cm = 3/100m = 0.03m.
2? . ? 5 yuan? 18cm = 18/ 100m = 0. 18m。
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decimal point