Understand decimeter, millimeter, kilometer 1, decimeter is expressed by the letter dm, decimeter 1 is written as 1dm.
2. Millimeter is expressed by the letter mm, and 1mm is written as1mm.
3. Kilometers are represented by the letter km, and 1km is written as 1km.
Conversion between meters, decimeters, centimeters, millimeters and kilometers
1, 1cm= 10mm or 1cm = 10mm.
2. 1 decimeter =10cm or1DM =10cm.
3. 1m = 100 cm or 1m= 100cm.
4. 1m = 10 decimeter or 1m= 10dm.
5. 1 km = 1 000m or1km =1000m.
The actual length is between 1 decimeter, 1 mm and 1 km.
1, the thickness of an IC card is about1mm.
2. The length of 1 sleeper is about1decimeter.
3. The distance between two bus stops is about 1km.
4, according to the specific situation to choose the appropriate length unit.
How long is this pencil (decimeter, millimeter)?
Knowledge points:
Through actual measurement, understand the relationship between meter, decimeter, centimeter and millimeter.
1 decimeter = 10 cm or1DM =10cm;
1m = 10 decimeter or1m =10 DM;
1cm= 10mm or1cm =10mm;
2. Know the actual length of 1 decimeter or 1 millimeter.
3. You can use the relationship between length units for unit conversion.
How long is 1 km (km knowledge)
Knowledge points:
The length of 1. Experience 1 km.
2. Understand the relationship between kilometers and meters; 1 km = 1 000m or1km =1000m.
3, can correctly use the length unit.
Understanding of 1, mm and decimeter;
(1) Estimate the length of common objects in centimeters, and deduce the length units of millimeters and decimeters in actual measurement.
(2) Through the measurement activities, we can actually feel how long 1mm and 1mm are, and we will use millimeters and decimeters as length units to estimate.
(3) Knowing the forward speed between meters, decimeters, centimeters and millimeters, we can choose the appropriate length units according to the specific situation and will use these length units for measurement.
(4) Be able to complete relevant calculations and applications, and develop the concept of space and hands-on operation ability.
2. Understanding of kilometers:
(1) Understand that "kilometer" is a much larger unit of length than "meter", know how long 1 kilometer is, and get a preliminary understanding of the application of kilometer in life.
(2) Grasp the propulsion rate between kilometers and meters, correctly convert and calculate, and solve related practical problems.
3, tons of understanding:
(1) Understand that "ton" is a much larger mass unit than "kilogram", know how much 1 ton weighs, and understand the application of the mass unit "ton" in life.
(2) Grasp the forward speed among tons, kilograms and grams, correctly convert and calculate, and solve related practical problems.
(3) The quality of some common items can be estimated, and the appropriate quality unit can be selected according to the specific situation.
Understand the knowledge points of millimeters and decimeters
target
1. Understand the length units of millimeters and decimeters, and initially establish the length concepts of 1mm and 65438+ decimeters.
2. Know 1 cm = 10 mm 1 m = 10 decimeter 1 decimeter = 10 cm.
focus
Make students know the length units of millimeters and decimeters, and initially establish the length concepts of 1mm and 1mm, knowing that 1cm = 10mm =10 mm =
difficulty
Help students to establish the concepts of length of 1 mm and 1 decimeter, form representations, deepen their understanding of the concepts, and correctly express the length of objects by using the concepts.
Classroom practice
1. What are the commonly used length units for dictation? And gesture it.
2. What is the relationship between the commonly used length units in dictation?
Measure the length of the pencil on the same table.
4. Is the following statement correct?
Crayons are 6 mm long.
Jumping rope is 2 cm long.
This table is seven meters high.
Chalk is 75 decimetres long.
Kilometer knowledge point
The understanding of kilometers belongs to the field of mathematical space and graphics in primary schools. Kilometers are relatively large units of length, and two examples are arranged in the textbook. Example 1 arouses students' initial perception of 1 km mainly through the theme scene diagram and the activity scene created in the example. Example 2 By creating a scene of practical activities, students can further experience and feel the length of 1 km while walking, thus actively constructing the concept of the length of 1 km and leading it to 1000 m = 1 km. The textbook has designed a number of life-oriented activities to enhance students' perceptual knowledge of kilometers and develop students' spatial concept as much as possible.
Key points and difficulties:
The key points of teaching are: to perceive and understand the meaning of kilometers, to establish the concept of 1 kilometers, and to know that 1 kilometers = 1000 meters, and kilometers are converted into meters.
A large number of knowledge points
1. Make students know the weight unit of tons and the application of tons in real life, and initially establish some concepts of heavy objects 1 ton, knowing that 1 ton = 1000 kg.
2. Distinguish the quality units and choose the quality units flexibly, which will make a simple conversion between tons and kilograms.
3. Cultivate students' abilities of observation, comparison and abstraction, and develop their spatial imagination.
4. Strengthen the training of number sense and feel that the knowledge of mathematics is around.
According to the age characteristics of students in grade three, T is personified, and T's self-introduction is presented by courseware, so that students can make friends with T. The courseware demonstrates 100 bags of cement, 20 bags of 50 kg rice and 40 bags of 25 kg flour. Let students intuitively perceive that 1000 kg is the concept of 1 ton.
~ ~ ~ Exercise ~ ~ ~
1.
( 1)6 kg = () g。
(2)34000 kg = () tons
③8 tons = () kg = () g.
(4) 48,000 kg = () tons = () grams