The first teaching content:
Page 26 of the first volume of grade four, case 1 case 2, do it.
Teaching material analysis:
In the example, only the example of addition and subtraction is presented, and the key number corresponds to the result displayed on the screen; French multiplication and division problems should be tried by students themselves. When calculating large numbers with a calculator, let students explore the law of calculation, and organically combine calculation with exploration law, which can not only let students learn how to calculate with a calculator, but also stimulate students' interest in exploring mathematical mysteries, and is also a direct way to cultivate students' ability of observation and reasoning.
Teaching objectives:
1. Enable students to make simple calculations with electronic calculators.
2. Let the students know that the order of calculation with an electronic calculator is the same as that of writing.
3. Let students be good at observing and discovering the secrets of mathematics, and be able to do oral calculations on some regular numbers.
Teaching focus:
Able to do simple calculations with a calculator.
Teaching difficulties:
Know how to observe and find some regular numerical calculations.
Teaching process:
First, use a calculator to calculate.
1, Teacher: Who can calculate with a calculator?
Students introduce how to use it: press the on/c key to display: 0 Enter the topic, press the = key to display the result, and then press the on/c key to clear the screen.
2, display: 386+ 179 =, students try to calculate with a calculator.
Tell me how you use a calculator to calculate.
(Press "386" first, the screen will display 386, then press "+",the screen display will remain unchanged, then press "179", the screen will display 179, and press "=" to display the result 565. )
Try what function the CE key has. (clear)
3. Try it yourself
26×39=3 12÷8=
What do you think should be paid attention to when using a calculator?
Look at the number clearly and don't press it wrong; Please clear the screen before each calculation.
5. calculation.
765+469=589×76=3208-2965=625÷25=6848-579+386=
Re - calculation
946×57×0= 100÷5=3028-2965=
Estimation: 99+ 199 ≈.
It's over. Tell me how you calculated it. What do you want to tell everyone?
It is not always possible to calculate with a calculator. For example, you don't need a calculator for problems that can be calculated directly with your mouth and simplified. )
6. See who counts fast and practice.
7. Do "Do" on page 26.
Let the students do it in groups and then do it at the same table.
Second, it is observed that
1, compare and see who did it right and fast. (Group of four)
9999× 1=9999×2=9999×3=9999×4=
2. Observe the above formula and results. What pattern did you find?
Teacher: According to your findings, can you write the answers to the following questions directly without using a calculator?
9999×5=9999×7=9999×9=
Teacher's summary: When you meet a natural number (except 0) within 9999 times 9, the answers are all five digits, the digits and units are the product of natural number and 9, and the middle three digits are all 9.
3. Complete "Done" on page 27.
Third, practice.
Basic exercises
1, explore the law with a calculator
1 1 1 1 1 1 1× 1 1 1 1 1 1 1=?
2, the magical 198.
32 1- 123=654-456=987-789=95 1-753=357- 159=9856-9658=8745-8547=54 12-52 14=
(2) Consolidate exercises
1. Go into life and solve problems.
Teacher: Now let's study a very valuable problem.
A faucet that is not turned on correctly will drop about 12 kg of water every day, and the water will flow away in vain.
◆ According to this calculation, a faucet that is not tightly closed will waste _ _ _ _ _ kilograms a year (calculated in 365 days).
◆ Put water in a drinking bucket (20kg per barrel), which can hold about _ _ _ _ _ _ barrels.
◆ If a family of three uses 6 barrels of water every month, the water will last for _ _ _ _ months, about _ _ _ _ years.
(1) Students use calculators to input data, work out figures, and then report the results by roll call. The teacher reminded the students to read the data clearly and enter it correctly.
(2) What do you want to say after reading these data?
(3) Summary: Water conservation should start from dribs and drabs. There is an advertisement saying: "When there is only the last drop of water left in the world, it is your own tear!" " Let's start from ourselves, try to be a thrifty boy and do our part to create a harmonious and economical society!
2. Exercise 3, question 12.
It is required to calculate in writing before checking with a calculator. Students should pay attention to the appropriateness and correctness of the corresponding data when filling out the form after calculation.
3. Exercise 3, question 14.
This is a conventional calculation problem, which is faster than a calculator with a simple method, reflecting the flexibility of the calculation method.
(3) Expanding exercises.
What is the result of 8765-32×2 1? How do you operate it?
1, students operate independently and report by name.
2. The teacher introduced the usage of "M+" and "MR"
Press 32×2 1 first, and the number is 672. Then press "M+" so that the answer can be saved, then press "8765-" and then "MR" to call up 672, and finally we can get the answer 8093.
Fourth, class summary.
What did you buy today?
Fifth, homework.
Exercise 3 questions 1 1 and 13.
Chapter II Teaching Objectives:
1, know electronic calculator, and can use calculator to perform four operations on large numbers.
2. I will use the calculator selectively according to the characteristics of the topic;
3. Let students experience the process of exploring simple mathematical laws with calculators, and cultivate their abilities of observation, induction, generalization and reasoning;
4. We can have a preliminary understanding that the calculator is only a calculation tool, and the human brain has incomparable advantages compared with it.
5。 Carry out mathematical culture education
Key points and difficulties:
Will use the calculator selectively according to the characteristics of the topic;
You can explore simple mathematical laws with a calculator and realize that the calculator is only a calculation tool, and the human brain has unparalleled advantages compared with it.
Teaching preparation:
Courseware and calculator
Teaching process:
First, situational introduction
Teacher: Please watch a video (the development of computing tools).
Teacher: What computing tools were mentioned in this video just now? (Show floor plan and abacus diagram)
Teacher: The first computer was born in America in 1945. 1977 After the first microcomputer came out in Japan, computers became a common tool for people to calculate.
(Courseware shows all kinds of commonly used computers)
Teacher: Where have you seen someone use a calculator? Can you use it?
Second, use a calculator.
1, Introduction to Calculator
Do you know the name and function of the middle button of the calculator? Please introduce yourself to each other (Then ask one person to come on stage and demonstrate the number keys, symbol keys and function keys with the presenter. What are the functions OF on, of, AC, CE and C? How do you want to press it Number-symbol-equal sign-clear)
We all know how to use a computer, so let's use a calculator to calculate in this lesson. (blackboard writing topic)
2. Try to practice and standardize the operation.
There are 775 students in Yinpenling Primary School. If you save 1 kg of water per person per day, you can save 775 kg of water per day. How many kg of water can you save every year (365 days)?
(1) named oral expression
(2) Students' trial calculation
(3) Report the results and correct the mistakes.
(Computer) saves 282,875 kilograms a year. If a family of three uses 25 kilograms of water every day in a water-deficient area, how many days will this water be enough for them?
Student trial calculation
(Computer)115131How many years is 365 days a year?
Student trial calculation
Teacher: We have done so many questions, but do you think it is difficult? What do you think are the advantages of using a calculator?
3, flexible use
See who is right and who is quick!
(1) Students' calculation and teachers' patrol guidance
2 19×35=4 1600÷ 128=24÷6= 125×8= 138976- 138970= 1379+34089=
(2) Student reports and collective corrections.
Teacher: Are all these questions worked out with a calculator? What is useless? Why?
(3) Summary
Teacher: What kind of questions do you think are suitable for calculation with a calculator?
Third, the ability to improve.
Teacher: Do you want to work out a big and difficult problem? Let's play a game that challenges the limits.
Let's use 9 as the multiplier. How many nines do you want to take? Small, eight nines.
999999999×999999999=
test
Reported figures
Do you think the calculation result is correct?
What difference do you see on the calculator? By the way, e is the wrong abbreviation of English words. Do you know what this word means? No!
Teacher: That teacher can know that this result is wrong without looking at this E. Do you know where I saw it?
Teacher: Yes, because all tools have their limitations. Now that we have only a few calculators in our hands, it seems that we can't do this problem.
Laozi said: it is easy to be difficult in the world, and the major events in the world must be detailed. Don't worry, this number is too large. Can it be counted if it is smaller? Then let's start with something simple and see if we can find anything.
Calculation: 9*9=8 1
99*99=980 1
999×999=99800 1,
9999×9999=9998000 1
Many students raised their hands. What are you going to say?
Find a pattern and draw a conclusion.
999999999×999999999=99999999800000000 1
Do you have any ideas after doing this problem?
Teacher, yes! We can use our smart minds to solve problems that calculators can't solve, so be proud of ourselves! But didn't our calculator play any role in the calculation just now?
Teacher: Yes, he can help us explore legal tools. In fact, the calculator in our hand can't calculate because of the small number of digits, but there are still tools to calculate, such as the demonstration of the computer teacher we have in the classroom now.
Now 64-bit calculators have been used in many industries. Even so, can the calculator solve all the problems?
Teacher: Tools have their limitations and need to be continuously developed. It seems that tools are not the most important thing in both study and life. What is important is that human wisdom is the greatest strength under natural enemies. (Show Bacon's famous words)
I hope the students will become smart people.