Second, teaching material analysis: Choose the meter ruler as an intuitive teaching aid, and take the length unit as an example to illustrate that decimal is actually another representation of decimal fraction. Through three levels, students can further realize that rewriting a lower unit number into a higher unit number can be expressed by fractions with denominators of 10, 100 and 1000, and such fractions can be expressed by decimals.
Third, the analysis of academic situation: "The meaning of decimals" is the first lesson in the third unit "The meaning and nature of decimals" in the second volume of the fourth grade of People's Education Press. For the meaning of decimals in grade four, students have initially understood decimals and fractions, which is the direct cognitive starting point of students. The above two points are far from the teaching of this course for a long time, and students have no systematic knowledge of fractions, so the content of decimals is more abstract. How to properly handle the teaching of decimal meaning in grade four has become the focus of this unit.
Fourth, the teaching objectives:
1. Understand and master the meaning of decimals.
2. Experience the close relationship between decimals and daily life, enhance the consciousness of independent inquiry and cooperation and exchange, and establish the learning confidence of learning mathematics well.
Five, teaching difficulties:
Understand the meaning of decimal.
Sixth, the teaching process:
An exciting introduction
Teacher: Teacher, here is a ribbon. How long is it?
Teacher: How do you estimate it? How many meters is the extra part? (Then measure) How many meters is 1 decimeter?
Teacher: How long is 0. 1 meter? What other numbers can you use? 1 decimeter =0. 1 meter, which we learned in grade three, remember? (The courseware shows the meter ruler and asks how to calculate 0. 1 meter? )
(2) Explore the meaning of decimals.
Know 0. 1.
Teacher: 0. 1. There are many things in life.
(1) Play onion class. Activity arrangement: the dog's arm is 4 cm, the finger is 6 cm, and the eyelash is 3 mm.
Teacher: "Is there 0. 1 in it? Tell me how they all got it? "
(2) The content of students' exchange activities.
(3) Teacher: Now can you tell me how 0. 1 came from? What do you mean?
The teacher summed up the meaning of 0. 1: divide "1" by 10, take 1 as one tenth, and use decimal number 0. 1.
Follow-up: Can you find other 0. 1 on this line segment?
Teacher: Can you find 0.2? How many zeros are there in 0.2?1? How to express it in fractions?
What about 0.9?
Teacher: Decimals with only one decimal place like this are called decimals.
Teacher: 1 How many zeros are there?1? (10 0. 1) Let's count them together.
Exercise: the question 1 in the exercise list (let students fully feel that 0. 1 is obtained by dividing "1" equally into 10).
(4) Explore 0.0 1
Do you know the meaning of 0.0 1?
Teacher: Can you find 0.0 1 meter on the ruler?
Teacher: Divide "1" into 100, and take 1 as a percentage, with 0.0 1 as a decimal.
Teacher: Is this square still 0.0 1? (Yes 100 0.0 1) Are there any other decimals?
Teacher: Are they all composed of several 0.0 1
Decimals with two digits after the decimal point like this are called two-digit decimals. Two decimal places are composed of several 0.0 1, so the counting unit of two decimal places is 0.0 1.
The courseware shows 0. 1 in the box.
Teacher: How many 0.0 1 are there in this 0. 1? Can you count?
0. 1 contains 10 0.0 1. 10 0. 1 just now is 1. Now, 10 0.0 1 is 0. 1. What is the progressive rate of counting units near decimals? (The student's guess is 10)
Teacher: Let's take this and guess if it is 10.
(5) Explore 0.00 1
Teacher: Guess how many decimals we are going to learn next? Which number should we start with? Do you know the meaning of 0.00 1? The length of eyelashes can be recorded as 0.00 1.
Teacher: Besides 0.00 1, which three decimal places do you know? Can you introduce it?
Teacher: How many 0.00 1 does 0.274 consist of?
Teacher: 10. How much is 0.00 1? Why?
Summary: Each counting unit is divided into 10 by the previous counting unit, so the progress rate of counting units adjacent to decimals is also 10.
(3) Consolidate exercises
(4) Summary
What did you get from this lesson?