In this lesson, students can fully experience the process of estimating and measuring the length of an object through the change of the golden hoop, and draw decimeter and millimeter, so that they feel that the generation of decimeter and millimeter is the need of daily measurement. Then through the process of self-study, I found the relationship between the unit and the ruler from a ruler, and initially established the expression of decimeter and millimeter. By applying what they have learned to solving practical problems, students can enjoy learning mathematics.

Teaching objectives

1. Know the length units of millimeters and decimeters, initially establish the length concepts of 1 mm and 65438+ decimeters, and know the rate of progress between units.

2. Cultivate students' hands-on operation ability and simple reasoning ability.

3. Infiltrate the idea that the length unit comes from practice and is applied to practice, and cultivate students' innovative consciousness and the ability to apply what they have learned to solve practical problems.

Important and difficult

Establish the representation of decimeter and millimeter in practical operation activities.

Establish the length concepts of 1 decimeter and 1 mm.

teaching process

Activity 1 Import Dialog Import Stimulate Interest

Teacher: Students, do you know me? Then where can you find information about me? Do we know each other now? Never realized that understanding is a kind of? Fate, since it is so predestined, I will show you something interesting. (takes out the golden hoop to demonstrate) Is it fun? Where is the fun?

Teacher: Now please estimate how long it is.

Teacher: How long? The teacher here has a ruler 1 meter long. Let's ask it to measure. First aim one end of the gold hoop at the zero scale of the ruler, and then look at the scale line at the other end. This is the length of this golden hoop, just right? 1 meter.

Teacher: The estimate is very accurate. The meter is the unit of length we used to know, and it is represented by the letter M. Which other unit of length have we made friends with? (cm) is represented by letters (cm). Do you remember the relationship between meters and centimeters? (1 m = 100 cm)

Teacher: It's amazing. Who can tell me how long 1 cm is? (Student demonstration, the width of the index finger nail) 1 meter? (Hands open)

Teacher: It's amazing! We have a ruler of about 1 m and 1 cm hidden on us.

Activity 2: Explore practice and learn new knowledge.

1, knowing decimeter

(1) Teacher: Just now, the students estimated the length of the golden hoop. Please pay attention. The golden hoop is going to change. How long has it been?

Teacher: Let's ask the meter ruler to measure it. Look, every square on this ruler is 1 cm. Let's count together, 1 cm, 2 cm.

Teacher: What do you think of this counting? Is there any good way? (10cm10cm)

Default: By the way, the number 10 cm 10 cm is much simpler than the number 1 cm 1 cm. What a coincidence. It seems that when measuring long objects less than 1 m, the ruler of 10 cm is also very necessary.

Teacher: Actually, 10 cm has another name in mathematics. What is this?

Teacher: Let's not jump to conclusions. Please turn to page 34 of the textbook, read the first part, circle the answers you think are possible and raise your hand.

Please answer and read what the wise old man said.

Teacher: By the way, students really know how to study. The decimeter is represented by the letter dm. Mathematically, we call 10 cm 1 decimeter, so we say 1dm= 10cm.

Teacher: 1 decimeter equals 1 0cm, so how long is1decimeter? Please find 1 decimeter from your ruler and communicate with your deskmate when you find it. 1 where is the decimeter? Student report.

Teacher: The students are really amazing. They all found 1 decimeter. Please look at the big screen. This is an enlarged ruler. Let's look for 1 decimeter. 0 0- 10/0cm is 1 decimeter.

Teacher: Please pay close attention to this line segment. How long has it been? what do you think? (1- 1 1 cm is 1 cm, which means1decimeter).

Teacher: You can not only observe, but also explain. It's amazing. What about now? (Clearly, as long as it is 1 0cm, it is1decimeter.)

Teacher: Looking for decimeter, what did you find?

Summary: No matter how you look at it, finding 1 0cm is1decimeter.

Teacher: The golden hoop has changed again. How long has it been? ( 10 cm)？ (1 decimeter) What about now? (2 decimetres) Why? Who would say? What about now? (3 decimetres, 4 decimetres, 5 decimetres) What did you find? (0 to dozens of centimeters is a few decimeters) What about now? (9 decimeters) Who said, look carefully, can you tell me how many decimeters 1 meter has? So we say 1 m = 10 decimeter.

Teacher: That's a good point. To understand 1 decimeter, we need to understand it from many angles. Think about it. Do we also have a ruler about 1 decimeter hidden on us?

Teacher: The students are really amazing. Now, please use a one-meter ruler to estimate the long side of your math book, then measure (26 cm), estimate the short side, then measure, and then measure the thickness of your math book?

2. Know millimeters

Teacher: less than 1 cm. how much is it?

Teacher: What did you find? Units smaller than centimeters can be used in millimeters.

Teacher: It's amazing. Open the second part of the book on page 34 and explore its secrets.

Teacher: What did you find? By the way, the cell 1 in 1 cm is 1 mm, and I know a new unit.

Blackboard: Mm-hmm.

Teacher: How big is 1mm? Let's get to know each other. Please find 1mm from the ruler and tell your deskmate where it is. Find another paragraph 1 mm and click it. Please look at the big screen. Let's go and find it together. (1 mm, 2mm ... 5mm)

Teacher: So 5 mm is 1 cm? Give you a cross section of 5 mm, can you draw the length of 1 cm? Then can you find 1mm according to 5mm? What's in 5 mm? (5 x 1 mm)

Teacher: Now? (1 0mm equals1cm)

Teacher's blackboard: 1cm = 10mm

Teacher: Do we also have a ruler about 1mm in our hands?

Teacher: The thickness of thumb nail is closer to1mm.. You see that we also have a 1 mm ruler hidden in our body. How amazing.

Teacher: Now please close your eyes and think1mm. What is 1mm in life? Let's take a look (picture display)

Teacher: Millimeter is a very small unit. We seldom use it when measuring the length and width of an object, but we can always see it when measuring the thickness of an object. Students, through today's study, we learned two more units of length. Do you know which units measure length now? Line up in the order from largest to smallest.

Activity 3 Practice knowledge combing and comprehensive application.

1. Now the teacher will draw one of 1 m, 1 decimeter, 1 cm, 1 mm on this piece of white paper. Guess which one I will draw? Why?

Please draw a line segment of 1 decimeter on white paper, a line segment of 1 cm on the line segment of 1 decimeter, and a line segment of 1 mm on the line segment of 1 cm. Look at these units of length. What do you want to say?

2. The length of the brothers' queue, how to tell who is who?

Blackboard reading, finger memory method (thumb is equivalent to kilometers, index finger is equivalent to meters, middle finger is equivalent to decimeters, ring finger is equivalent to centimeters, and little finger is equivalent to millimeters; Then the fingers are separated, and the thumb and forefinger are most separated, indicating that the permeability of kilometers and meters is 1000, and the other four units are almost separated, indicating that the permeability between every two adjacent units is 10. )

Step 3 correct mistakes

Different lengths, the same ability. Let's take a look at Mingming's diary.

I got out of the 2-meter-long bed this morning, picked up 1mm toothbrush, brushed my face, dried my face with a 70-meter-long towel, and went to school after breakfast. The school is not far from my home, about 900 mm When I came to school, I sat on a 5-meter-high stool and took out a 7-centimeter-thick Chinese book, ready to start my Chinese class.

Teacher: What problem did you find? Try to help him change. Why do you say that? Can you be specific?

Activity 4 Practice Summary

Who can tell me what you know in this course?

Length brothers get together. Who wants to name this class?

Activity 5 Homework

According to life experience, write an article about math diary with the units learned in this lesson.