Teaching objectives
Knowledge and skills:
Make students briefly understand the development of calculation tools, including ancient counting methods such as knotting, simple calculation knowledge, traditional calculation tools-abacus and its calculation methods, calculators commonly used in life, and the development history of modern computers.
Process and method:
Let students experience the process of understanding and using calculation tools, and use calculators to calculate.
Emotions, attitudes and values;
Cultivate students' interest in learning mathematics and feel that there is mathematics everywhere in life.
Emphasis and difficulty in teaching
Teaching emphasis: understand abacus, calculator and other computing tools.
Teaching difficulty: using calculator to calculate.
teaching tool
Ppt courseware
teaching process
First, the introduction of new courses.
As we all know, mathematics is always inseparable from calculation. In order to facilitate calculation, people invented many kinds of calculation tools. We have a simple understanding of the calculation tools in the second volume of Grade Two, Understanding Numbers within 1000. Today we will continue to understand the calculation tools. (On the blackboard) Who will tell us which calculation tools we have learned first?
Students introduce computing tools.
Second, introduce ancient computing tools to broaden our horizons. (Courseware demonstration)
(A) understand the calculation and preparation
Teacher: Since ancient times, computing tools have experienced a long development process with the continuous progress of human society. In ancient times, human beings had the need to count the labor of fishing, hunting and fruit gathering. People count by nicks on stones, knots or sticks. Later, there was such a counting method-counting. (blackboard writing: calculation and preparation)
Introduction to calculation and compilation: More than 2000 years ago, our people used calculation and compilation. A number is expressed in decimal system, which is used alternately vertically and horizontally. Single digits are represented by vertical lines, ten digits are represented by horizontal lines, and hundreds of digits are represented by vertical lines ... spaces represent zeros. Computing chips are generally made of bamboo sticks more than ten centimeters long (they can also be made of wood, bones or jade). Use these calculations to make them into different forms, represent different numbers, and carry out various calculations.
(2) Understand abacus
1. Introduce the origin of abacus: After a thousand years of calculation, China people invented the abacus as a calculation tool. As early as15th century, abacus was widely used in China, and later spread to Japan, Korea and other countries. It has the characteristics of simple structure and convenient use. Especially, it is more convenient to use it to calculate a lot of addition and subtraction. (blackboard writing: abacus)
2. Introduce the composition of abacus.
(1) abacus part name:
Teacher: The abacus is an ancient invention and a traditional calculating tool in China. It is widely used in production and life, and still plays its unique role. Where have you seen someone use an abacus? Chinese medicine shops, banks, etc. )
Do you remember the names of the abacus parts? Let's take a look again. A beam is installed in the rectangular frame of the abacus, and several sticks are drilled on the beam, which is called a file. Wear a string of beads on each string, which is called abacus or beads. The common abacus is two beads on the beam, each representing five; Five under the beam, one each.
Show two kinds of abacus on page 24 of the textbook: observe the difference. The abacus on the left is China's abacus, and there are two beads on it, each of which represents 5. Later, the abacus developed to Japan and gradually evolved to the right, with a bead on it. The reason is that in ancient China, when the cardinal number was 16 and 15, it was 15, so every gear of the abacus was 15. Decimal system was adopted after entering Japan, so there are 1 bead left on the abacus. First gear means 10. It is characterized by simple structure, convenient use and special practicality. It is more convenient for him to calculate a lot of addition and subtraction.
(2) Two functions of abacus: calculation and counting.
Teacher: An abacus has two functions: calculation and counting. When calculating, dial the abacus according to the prescribed method to get the calculation result. When dialing the number, you should set the number first, specify which gear it is, and then dial the number. Each gear on the abacus represents a number. We choose a file as a bit (make a mark) and count from this file to the left, that is, ten bits, hundreds of bits, thousands of bits, and ten thousand bits, which are exactly the same as the numerical order of integers. When all the beads are near the box, there are no numbers on the abacus. When counting, dial the beads against the beam. When picking the ball, you should dial it from the high position according to the number of digits. (The third gear from right to left is defined as one digit) Can you write down the numbers represented by the following abacus respectively?
(602 134067 352 15862)
(Design intention: Students have previewed and searched for materials before class, so at the beginning of class, students are allowed to show their known computing tools, which distracts students' thinking and improves their interest in learning. According to the students' feedback, the teacher asked the students to introduce the methods of knot and calculation of funds, which further made them understand the development process of calculation tools. )
(3) slide rule.
/kloc-At the beginning of the 7th century, the British invented the slide rule.
(4) mechanical calculator
/kloc-in the middle of the 0/7th century, Europeans invented the mechanical calculator.
(5) Electronic computers
In the 1940s, the first electronic computer was born.
(6) Understanding of calculators
In the 1970s, people invented electronic calculators and began to use calculators in their daily lives. As long as you enter a topic, the calculator will display the results and automatically complete the calculation process. This is very simple and quick. Let's learn to calculate with a calculator. (blackboard writing: calculator)
1, introducing function keys:
You may find many kinds of calculators. This is because there are different calculators according to different needs. There are scientific calculators and the simplest calculators ... but their functions are almost the same. Let's take a look at this calculator in our hand.
Autonomous learning and group communication: Do you know which buttons on the calculator keyboard and what are their functions? What is the "On/Off" key for? What does the "Close" key do?
(Design intention: Show the calculator in students' hands, so that students can have a preliminary understanding of the size, appearance and function of the calculator, and lay a foundation for learning the use of the calculator in the next step. And arouse the interest of exploration. )
2. Use a calculator:
Teacher: How to use the calculator?
Students introduce how to use it: press the "On/c" key to start displaying; Input numbers and symbols; Press the "=" key to display the result; Press the "On/Off" key again to clear the screen. There are also some keys with special functions on the calculator. Such as a,%, etc. , can also be used to calculate scores and so on.
3. Calculate with a calculator.
( 1)386+ 179 825- 138
First estimate, how much will this problem get? How to estimate? How to calculate with a calculator?
Practice: 4468+179232010-8925.
(2) Use a calculator to calculate multiplication and division.
Let's make a rough estimate of how much it is. How to estimate? Then use a calculator to calculate.
26×39 3 12÷8
(Design intention: Know the calculator, let students know the function of each function key of the calculator independently, and under the guidance of the teacher, use the calculator to carry out four operations and explore the operation rules, especially the use of the storage function key is more interesting and difficult. It can not only cultivate students' observation and reasoning ability, but also correct students' correct attitude towards calculators and know how to use them reasonably. )
4. Use a calculator to find out the rules.
9999× 1= 9999×5=
9999×2= 9999×7=
9999×3= 9999×9=
9999×4=
Practice independently with a calculator in the form of a competition.
Students calculate and communicate with the class.
Third, classroom practice to consolidate new knowledge
1, use a calculator to calculate the game.
55846+7646= 13027-8934= 66280×23=
6908×37= 1 1 1 1 1 1 1 1 1÷9= 3954 12+ 10589=
2, calculate, find the law.
1 1 1 105÷9=__________
9÷9= 1 1 1 1 1 104÷9=__________
108÷9=________ 1 1 1 1 1 103÷9=__________
1 107÷9=________ 1 1 1 1 1 1 102÷9=__________
1 1 106÷9=________ 1 1 1 1 1 1 1 10 1÷9=__________
Fourth, summarize and improve.
Teacher: The use of calculator brings us a lot of convenience. With the progress of science and technology, people invented electronic computers, desktop computers, notebook computers and tablet computers. With the development of society, human computing tools will be more advanced, which will be realized by all of you here-your generation.