1. Decimal can be divided into () parts, with decimal () on the left and decimal () on the right.
Second, judgment.
1. 100+0 equals 0. 1 ()
Third, choose
1.500g The price of lean meat is ().
A, 179 yuan b, 8. 1 yuan c, 35.5 yuan.
Fourth, application
Write the numbers that meet the following requirements with the numbers 3, 0, 7, 4 and decimal point. Each decimal point can only be used once (write 3).
1. Three decimal places less than 1:
2. Three decimal places less than 7:
3.0 unread two decimal places:
Fill in the blanks:
The last "5" in 1. 5.55 yuan means ()
2.0.6 kg = () g
Fill in the blanks:
1. Decimal is calculated by () ... or () () ...
2. One digit after the decimal point indicates (); Two decimal places indicate (); Three decimal places indicate ()
3. () There are four 1%
Application:
Please write down the following figures with the four numbers of 5, 6, 0 and 0 and the decimal point. Every number should be used and cannot be repeated.
Form a decimal () that does not read zero.
Synthetically read the decimal () of zero.
Read the fraction of two zeros ().
Fill in the blanks:
5 kg 506 g = () g.
Thinking mode makes students form a "convention", which naturally ignores the unit of "gram". Guide the students to read the whole question and analyze every little detail.
The sum of the internal angles of a regular hexagon is () degrees.
On page 29 of the book, "Practice Activities" guides students to explore and finds that the sum of the internal angles of a quadrilateral is 360. But hexagonal contact is less. In fact, it should be extended after class to form a perfect knowledge system, which is summed up as (n-2) × 180.
Judge:
Add 0 or remove 0 at the end of a number, and the size of this number remains the same ().
This problem is very chewy, and it can give birth to several "derivatives", which need to be sorted out and grasped macroscopically.
Select:
There are () two decimal places greater than 0.7 and less than 0.8.
Countless
To tell the truth, I made a mistake myself very carelessly for the first time! Shame!
Off-die calculation: (Simplify if you can)
16.8 1-(9.87-3. 19)
This kind of problem has always been my heart disease, and I believe it is also an urgent problem for many teachers to solve. At the same time, there are the following problems:
10-3.27-5.73
16.38-(6.38+2. 12)
3.78+2.86-0.78
The four of them are brothers.
A trapezoid is an equilateral quadrilateral.
Should I fill in (one set) or (only one set) this question?
Fill in the blanks:
Rewrite 8077000 into decimal with "ten thousand" as the unit.
In today's test, the error rate of this question is relatively high. Children will appear "80077000" and "8007700". On the surface, it seems that the examination of the problem is not rigorous. In fact, it is more because they have no clear understanding of this issue, which leads to blind completion. At the same time, the idea of changing the name by ten thousand units has not formed a system, or it is not perfect.
Drawings:
Draw an equilateral triangle.
On the surface, it seems to be a simple question, but in fact it is very technical. We should not just put down the practice of drawing, but should strengthen the operation practice here and establish a model to solve this kind of problem.
Application:
In an isosceles triangle, the degree of one inner angle is twice that of the other. What are the degrees of the three internal angles of this triangle?
Most students can solve one situation of this problem, but they haven't thought of the other, but we should give them such a problem, train them to think about the problem as comprehensively as possible, and make them think more thoroughly and carefully.
Two identical right triangles can be spelled into one () or ().
Triangles have () sets of corresponding bases and heights, and parallelograms have () sets of corresponding bases and heights.
An isosceles triangle with an internal angle of 60 degrees must be an equilateral triangle.
3.56+6.3-63.+3.56=
First, oral calculation.
3.2× 100 4.5×0.4 3.6×0.2 0.8× 1 1
3.5×2 0.25×0.4 1.4×0.6 0.4×25
4.2×4 5.6×0.3 5.5×0.2 2. 1×3
Second, vertical type.
28.2×30 3.92×27 3.28× 16 3.72×0.24 4.35× 12.96 5.4×0.6
Third, the column calculation
What is the 0.45 of 1? 34?
2.3. What is the 15 times of18?
The above is the test I spent 20 minutes on students today. 60% of the students in the class can do it completely right, but one child still made many mistakes. Her mistake is not a problem of counterpoint or decimal point, but an error caused by memory error or insufficient carry in multiplication. Then take immediate action to strengthen her weakness and let her slow down and sort it out bit by bit, and the effect will be much better. And gave her two questions:
6.58×4.5 24.5×0.9
9.99*4.85
10. 1* 15.6
Fill in the blanks:
2. 16×0.5 means ()
Maybe I didn't pay enough attention to this kind of problems when I studied this part of knowledge, or maybe I just emphasized the significance of multiplying decimal by integer and ignored the significance of multiplying decimal by decimal expression. So some children will have answers such as: 2. 16 is half, 2.06 is 0.5, or even 2. 16 is 0.5 times. Judging from the feedback of the topic, this really needs attention!
Judge:
1.0 1 times of a number must be greater than this number ()
At first glance, this question is really confusing. This requires cultivating students' ability to comprehensively analyze problems. At the same time, from the topic itself, it is necessary to understand the questioner's intentions and ideas, so as to understand the meaning well and make a correct judgment.
0.25 hours = () minutes
2: 45 = ()
I tested the children in Unit 3 yesterday. The error rate of the above two questions is relatively high. The children's answer is 25 minutes and 2.45 hours. To tell the truth, the students have little contact with the topic of time. Before, students were exposed to kilometers and meters, meters and decimeters, centimeters, tons and kilograms, kilograms and grams, square meters and square decimeters, and the entry rates of those were exactly 10, 100, 1000. Suddenly, 60% of students' enrollment rate is related to their maladjustment, or thinking mode. Without thinking, they "run amok". We should pay enough attention to it!
0.83m2 = () square decimeter
I practiced more rice and decimeters, tons and kilograms, kilograms and grams before. But after this problem appeared, some students had problems, and 8.3 was their answer. If it is normal to say that there are problems with the progress and speed at different times, then there is something wrong. Although only three or four students have problems, they are also very inappropriate. I also asked children why they made mistakes, and they would say they were careless. But I don't think that's why! How important it is to have a solid knowledge base! Or you'll hit a wall!
Select:
The product of 0.56×0. 15 is ()
A: 0.084
b、0.0084
c、0.00084
d、0.000084
Individual children will have the answer of B, because they also plausibly say, "Teacher, I see that the sum of the multipliers of 0.56×0. 15 is 4, and I just need to find the answer with four decimal places in the options." It suddenly dawned on me that the children were so thoughtful that they forgot that the product was "840"! Moreover, they are "opportunistic" without careful calculation. At the same time, how critical this "0" question is! It is worth reflecting on yourself!
To what extent do we grasp the significance of fractional multiplication?
For example, 10.26× 0.3
12× 10.33 How to explain their meaning?
According to 208× 145 = 30 160, write the following results directly in brackets.
2.08× 1405=( )
0.208× 14.5=( )
0.0208× 14500=( )
20.8×0. 145=( )
Although there are some changes in the way of doing the questions, on the whole, children have a solid grasp of the last three questions and can write accurate results directly as required. What gives me a new idea is to fill in the blanks first. Please take a closer look. It doesn't set questions according to the original intention, which we can understand as typos, but I prefer to regard it as a test of children's problem-solving ability, so I didn't make any special comments or change the questions, just let them do it themselves. In fact, some children saw it right away. It is also very gratifying to see the process of their solution, although it only accounts for a small part. It is very important to do the right questions, and more importantly, find the original problematic questions, rearrange and sort them out, so that children can really understand!
Decimal point 0.08 1 move two places to the left ().
0.08 1 minus 100 times is ()
This is a desktop problem. For other numbers, the calculation accuracy is good, but this is 0.0 1. In fact, the answers to these two questions are 0.0008 1, and children will write 0.008 1, and once the above answers are written wrong, the following "nature" will be wrong, all wrong! From this, we can see that the students have the same understanding of the meaning of "moving the decimal point two places to the left" and "reducing 100 times"-this is absolutely worthy of recognition. However, the concept of decimal point movement is not very clear, and there is no good targeted inspection and verification after calculation, which leads to "one mistake makes another"! Need to pay more attention!
Application questions:
My mother traveled to Thailand with the travel agency. She took 5000 RMB to the travel agency to exchange it for Thai baht. She intends to earn pocket money. How much Thai baht can she change? (Note before the book: 100 baht is equivalent to RMB 19.67)
This topic is the after-school exercise in the book. It seems difficult for students to solve the problem by doing the problem: 5000÷ 19.67, 5000÷ 100× 19.67 is their answer, and obviously they don't know the exchange rate, so I start with the wrong answer obtained by students and estimate it.
Fill in the blanks:
To calculate fractional multiplication, first calculate the product according to the law of (), then look at (), and point the decimal point () from the right side of the product. When the product has 0 after the decimal point, 0 () should generally be used.
This question looks really bad, but it actually introduces the calculation process of fractional multiplication. And it just hit the key point of students' poor language expression ability. Maybe the student can do it in the calculation, but if he is allowed to express or even write his own expression, it will not work, otherwise it will be incomplete, imprecise and full of loopholes! This requires strengthening the calculation process, understanding how it is calculated, improving and perfecting students' language expression ability, knowing the transfer of knowledge, and making the brain flexible.
Fill in the blanks:
To calculate fractional multiplication, first calculate the product according to the law of (), then look at (), and point the decimal point () from the right side of the product. When the product has 0 after the decimal point, 0 () should generally be used.
This question looks really bad, but it actually introduces the calculation process of fractional multiplication. And it just hit the key point of students' poor language expression ability. Maybe the student can do it in the calculation, but if he is allowed to express or even write his own expression, it will not work, otherwise it will be incomplete, imprecise and full of loopholes! This requires strengthening the calculation process, understanding how it is calculated, improving and perfecting students' language expression ability, knowing the transfer of knowledge, and making the brain flexible.
Fill in the blanks:
Move the decimal point 4.32 two places to the right and three places to the left, and the result is () times the original.
This question not only changed the narrative style, but also set some obstacles for children to fill in the blanks, so more children directly wrote the answer "10". And "0. 1" and "110" seem strange to them.
The extension of 89m is 8.9km, and 8.9km is () km () m.
The last empty child still wrote "9", which made him very depressed. Composite number is a difficult point, just like many complicated and tedious things in life!
Select:
The following figures, can get rid of "0" is ()
Answer: 3.00 0.300
b、 1.8000 5.00
c、5.780 0.0040
102.020 60.06
Most students will choose one more question. Is it related to some problems in the expression of this question? It may hinder students' understanding to some extent.
Through the results, we can see that my students still have a lot to do:
fill (up) a vacancy
9 square kilometers = () square meters
This problem can be traced back to last semester. When learning this part of knowledge, it is of little significance in real life, especially the relationship between different units is not very good, so after a long time, you will be caught off guard and the answer will not be effective. So review the past, clarify the relationship and improve the knowledge cognition system.
Three-dimensional graphics The shape seen from above is four horizontally placed squares, and the shape seen from the right is four vertically placed squares. Building such a three-dimensional figure requires at least () small cubes and at most () small cubes.
To tell the truth, this kind of question is rare in practice, but it adds a strange question to your own question bank, which will really be of great benefit to students. Therefore, before the explanation, let the students imagine and express, and then put the objects in the process of placing, explore, deduce and verify, and get the correct results through more comprehensive consideration. The effect is good!
Simple calculation:
70500÷250
On the surface, I like this question very much. It seems to be a very common problem. There are more than one method for children, but some methods will make students' calculations more and more troublesome and unable to extricate themselves. In actual combat, it is undeniable that students have better simple calculation methods, but teachers should also have some guidance to guide students how to do it, which can be simpler and more convenient, so as to understand the purpose and significance of simple calculation more deeply.
Fruit farmers should pack 680 kilograms of grapes into cartons and transport them away. Each carton can hold 15 kg. How many cartons do you need?
There are four options: 47 \ 46 \ 45 \ Cannot be calculated. [
Practice related to fractional division
Divide 8.76 by 5.3 to one decimal place, the quotient is 1.6, and the remainder is ().
A, 28 B, 2.8 C, 0.28 D, no residue.
Divide 8.76 by 5.3 to one decimal place, the quotient is 1.6, and the remainder is ().
A, 28 B, 2.8 C, 0.28 D, no residue.
Personally, I think there are two ways to think about this problem. One is to do it in a specific way of thinking, such as vertical calculation. When there is a remainder, the position of the decimal point should be determined according to the original dividend, but this method is basic, easy to understand and difficult to master.
In the process of making students fully understand, a classmate suggested that it is best to understand it according to the relationship between the parts of division with remainder, that is, the divisor subtracts the divisor and then multiplies the quotient. Of course, this method is difficult to understand, but easy to master.
45.6 This number is enlarged by 10 times () and reduced to 100 times ().
17/ 1000=
Students' habits expressed in decimals are 0. 17.
15.9 / 15=
The student's problem is that there are 0 problems in the middle of business that can't be handled well, and they will know what to do if they are not divided enough. Try the last question on page 6 1.
54/36=
After getting the remainder of 18, the students don't know how to continue the division. In teaching, teachers should pay clear attention to the writing format.