Question 2: The significance and nature of mathematical decimals in the second volume of the fourth grade. Summary of small knowledge points. Meaning of decimal: the denominator is 10, 100, 1000 ... can be expressed in decimal.
Properties of decimals: Add 0 or remove 0 at the end of decimals, and the size of decimals remains unchanged.
Question 3: The meaning and nature of decimals are the contents of several grades in People's Education Press. Instructional design of the meaning and nature of decimals.
Teaching content: the meaning and nature of decimals, the fourth grade of primary school mathematics.
Teaching objectives:
1, understand and master the nature of decimals;
2. Being able to simplify and rewrite decimals by using their properties;
3. Cultivate students' ability to summarize, analyze, synthesize and flexibly use what they have learned.
Key points of teaching materials: Through exploration, we can find the nature of decimals, and use the nature of decimals to solve related problems.
Teaching difficulty: Understanding the concept of decimal nature is the difficulty in this section. Teaching process:
First, the introduction of new courses.
In shops, the price tag of goods is often written in decimal places like this: gloves are 2.50 yuan, towels are 3.00 yuan. How much are 2.50 yuan and 3.00 yuan here? (2.50 yuan is 2 yuan 50 points, and 3.00 yuan is 3 yuan) Why can you write like this? This is an important property of decimals, and it is also what we are going to learn today. We will write "the property of decimals" on the blackboard.
Second, learn new knowledge.
1, study the properties of decimals.
(1) (blackboard "1") Teacher: At the end of "1", add 1 "and two" 0s "in turn. Has the number changed? How to change it? Can you fill in the appropriate unit name in brackets to make the following equation hold?
1( )= 10( )= 100( )
It is concluded that: 1 yuan = 10 angle = 100 point.
1 m = 10 decimeter = 100 cm
1 decimeter =10cm =100mm
Show me the meter scale. 1 decimeter is110 meter. What decimal numbers can you write? (0. 1m)； 10cm is101100m. What can be written as a decimal number? (0. 10 m), 100 mm is10011000 m What can be written as a decimal? (0. 100 m)
Blackboard: Because 1 decimeter =10cm =100mm.
So 0.1m = 0.10m = 0.100m.
Teacher: Are 0. 1, 0. 10 and 0. 100 equal? Why?
(blackboard writing: 0.1= 0.10 = 0.100)
A, looking from left to right, what is the situation? (Add "0" after the decimal point, and the decimal size remains unchanged)
B, looking from right to left, what is the situation? (Remove the "0" after the decimal point, and the size of the decimal point remains the same)
C, from this, what rules have you found? (Add "0" or delete "0" at the end of the decimal, and the decimal size remains the same)
(2) Display: 0.3 yuan, 0.30 yuan Teacher: Are these two numbers equal? Tell me why. (Students communicate, and teachers guide them appropriately and timely)
(3) Ask students to represent 0.30 and 0.3 respectively on two square papers of the same size (one of which is divided into 100 squares and the other is divided into 10 squares), and compare their sizes, showing that 301100 is three1.
(4) Teacher: What if you add two zeros and three zeros at the end of them? Are they equal? Why?
(5)0.03 plus "0" is 0.3, has the size changed? Why?
(6) Guide students to summarize the nature of decimals.
2. The application of decimal property
Teacher: According to this property, when there is a "0" at the end of the decimal, it is generally possible to remove the "0" at the end and simplify the decimal.
(1) Simplified decimal number Example 6: Question: Which "0" can be removed from the price list?
Q: What is the basis for this? After understanding the meaning of the question, the students answered and the teacher wrote on the blackboard: 2.80 = 2.84.00 = 410.50 =10.5.
(2) Rewrite the integer or decimal to the decimal of the specified number.
Teacher: Sometimes, you can add "0" after the decimal point; You can also put a decimal point in the lower right corner of the integer, and then add "0" to write the integer as a decimal.
For example, 2.5 yuan = 2.50 yuan and 3 yuan = 3.00 yuan.
(3) Give it a try.
0.4=0.400 3. 16=3. 160 10= 10.000
Practice: Answer the second question of "Practice" orally.
Discussion summary: When rewriting decimals, we must pay attention to the following three points:
A, do not change the size of the original number;
B only "0" can be added after the decimal point;
C. When rewriting an integer into a decimal, you must first add "0" after the decimal point in the lower right corner of the integer. (Think about why)
Third, consolidate the practice.
(1) According to the nature of decimal system, when there is a 0 at the end of decimal system, the end can generally be removed.
0. would you like to have a try？
Show the layered test card. Page 34 Basic Exercise 2. Which of the following numbers can be 0 >>
Question 4: What is the meaning of decimals? Meaning of 20 decimal places: the denominator is 1 float, 100, and the fraction of 1000 can be expressed in decimal.
Properties of decimals: Add 0 or remove 0 at the end of decimals, and the size of decimals remains unchanged.
Question 5: The significance of mathematical decimals in the second volume of the fourth grade. (10)
2.5 1× 10= 2.63× 10= 0.645× 1000= 0.03× 100=
4.03÷ 10= 7÷ 100= 63.5÷ 1000= 5.63× 10÷ 100=
0. 1÷ 100= 1.02× 10= 2. 1÷ 1000= 0.56÷ 10× 1000=
Second, I'll fill it out. (20)
1, a decimal consists of (), () and ().
2. The second digit to the left of the decimal point is (), its counting unit is (), the fourth digit is (), and its counting unit is (). The first digit to the right of the decimal point is (), its counting unit is (), and the counting unit of the third digit is ().
3. The decimal 2.05 is pronounced as (), 2 means () and 5 means ().
4. Three 1, five 0. 1 and 1 0.0 1 are written as a decimal ().
The counting unit of 5 and 8.02 is (), and it has () such counting units. The counting unit of 0.256 is (), and it has () such counting units.
6. There are () decimal places greater than 8 and less than 9.
7. Rewrite 168000 into a number with "ten thousand" as the unit (); The mantissa after omitting ten thousand digits is (); Rewrite 995,000,000 yuan into a number () with "100 million yuan" as the unit, and keep one decimal place as ().
8. If the decimal point moves one place to the right, the original number is (); if it moves two places to the left, the original number is ().
9. Enlarging () times 1.5 is 15, and reducing () times is 0.0 15.
Reducing 0.73 to one tenth of the original is ().
10. Fill in ">", "
0. 18○0. 179 0.50○0.5 0. 1○0.0999
4.954 6.96 6.8 hectares 6 hectares 8 square meters 108 cm 1 decimeter
Thirdly, I will be a judge. (6 points)
1 and decimal are both less than 1. ()
2. Kobayashi's height is11.4m. ()
3,0. 14 Pronunciation: 0.14 ()
4.0. 1 is one tenth of 1 and is 0.0 1 0 times of1. ()
5. Write 6 as 0.06 with two decimal places. ()
6. Add "0" or remove "0" after the decimal point, and the size of the decimal point remains unchanged. ( )
Fourth, I will choose. (5 points)
1, in the following figures, the same size after removing 0 is ().
A, B, C, 4400.
There is a () decimal between 2.0.5 and 0.6.
A, 0 B, 1 C, countless.
3. The closest to 6 is () a, 5.899 B, 6.0 1 C, 6. 1.
4, in 3.2, 3.02, 3.202 is the smallest ()
a、3.02 B、3.2 C、3.202
5. If the decimal point of a decimal number moves two places to the left, the number will be ().
A, expanded to 100 times the original number b, reduced to 100% of the original number.
C, reduced to one hundred percent of the original quantity.
5. Unit conversion. (8 points)
2. 1 yuan = () yuan () min 3.08km = () m.
8 m 6 cm = () cm 0.4 m2 = () cm 2.
2 tons and 20 kilograms = () tons and 0.5 hectares = () square meters.
1:30 = () 260m2 = () hectares
6. Colors indicate the following decimals: (6 points)
0.4 1.5 0.06 m
Seven, write the decimal point pointed by the arrow. (4 points)
Eight, write the number as required. (6 points)
Keep the whole number accurate to the tenth place, and keep two decimal places rounded to thousands.
3.5672
10.092 1
9.9985
Nine, according to the following figures: (10)
1、 0.76、 0.067、 0.706、...& gt& gt
Question 6: The meaning of decimals in grade four and the difference between reading and writing and grade three. ( 10) 2.5 1× 10 = 2.63× 10 = 0.645× 1000 = 0.03× 100 = 4.03 ÷ 65438+.0 ÷ 100 = 1.02× / Kloc-0/0 = 2.1÷1000 = 0.56÷10×1000 = 2. (20)1,and a decimal number is (). 2. The second digit to the left of the decimal point is (), its counting unit is (), the fourth digit is (), and its counting unit is (). The first digit to the right of the decimal point is (), its counting unit is (), and the counting unit of the third digit is (). 3. The decimal 2.05 is pronounced as (), 2 means () and 5 means (). 4. Three 1, five 0. 1 and 1 0.0 1 are written as a decimal (). The counting unit of 5 and 8.02 is (), and it has () such counting units. The counting unit of 0.256 is (), and it has () such counting units. 6. There are () decimal places greater than 8 and less than 9. 7. Rewrite 168000 into a number with "ten thousand" as the unit (); The mantissa after omitting ten thousand digits is (); Rewrite 995,000,000 yuan into a number () with "100 million yuan" as the unit, and keep one decimal place as (). 8. If the decimal point moves one place to the right, the original number will be (), and if it moves two places to the left, the original number will be () 9. Enlarge () times 1.5 to 15, and reduce () times to 0.0 15. Reducing 0.73 to one tenth of the original is (). 10. Fill in ">", "