Teaching objectives
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4. Understanding the meaning of multiplication and division through cooperative learning and independent inquiry can correctly train students' thinking flexibility and flexibly use various methods to calculate multiplication and division, thus cultivating students' friendly and cooperative consciousness, inquiry spirit and practical ability. Create situations to stimulate students' interest in learning mathematics and let them feel the calculations related to learning mathematics. The existing algorithms are diversified.
The fun of.
Teaching focuses on guiding students to discover, ask and answer questions.
Difficulties in teaching have solved the same problem in many ways.
Prepare courseware, school tools, corn, bananas, oranges and other fruit cards for teaching.
teaching process
First, create situations and introduce new lessons.
Teacher: A day's plan lies in the morning, and a year's plan lies in the spring. (Animation demonstration) In spring, the industrious bear planted some corn, and in autumn, the corn planted by the bear was harvested. Please look at this picture carefully. What mathematical information can you get from the picture? Can you ask a math question? (Student: There are four corn trees, each with three cobs)
Health: How many cobs does a * * * have?
Teacher: Can you list the formulas?
Health: (emoticon): 3× 4 =? 4×3=? 3+3+3+3=?
Flexible use of the theme map of the text to create a relaxed, vivid and vivid teaching situation.
Stimulate students' interest in learning and let them actively participate in learning. )
Second, independent exploration, cooperation and exchanges
Teacher: Seeing that his corn was ripe, Little Bear broke off 1 corn cob and walked back happily. At the same time, the animation shows 1 corn is missing 1 corn cob, with 1 corn cob on the bear's shoulder. )
Teacher: Can you put forward a math problem according to the meaning of this picture?
Health 1: The bear broke off one. How many people are there?
Health 2: How many cobs are left?
(blackboard writing: how many corn cobs are left? )
Teacher: How to solve this problem? You can use your own brain to think about it first, or you can wear it with school tools and communicate with each other in the group. (Students discuss in groups. )
Group report solution: (The teacher writes it on the blackboard)
3+3+3+2= 3×3+2=
3+3+3+3- 1= 4×3- 1=
Teacher: Please observe the listed formulas carefully and think about the characteristics of the formula on the right and how it is different from the formula on the left.
Health: There is only addition and subtraction in the left column of the formula, and there is no multiplication.
Health: In the formula on the right, there are multiplication, addition and subtraction.
Teacher: We have learned the formulas of addition and subtraction and mixed addition and subtraction before, so today there are formulas of multiplication and addition or multiplication and subtraction called multiplication and division, addition, multiplication and subtraction. Today we will learn to multiply, add, multiply and subtract. (blackboard writing topic. )
Teacher: Just now, the students were great. Before they learn, they can list multiplication, addition, multiplication and subtraction according to the pictures.
The formula of. Who can tell us how he came up with it?
Health 1: The first three corn trees have three sticks each, and the last one has two, so the formula is 3×3+2.
Teacher: (Draw a horizontal line under 3x3) What does 3x3 want in the picture?
Health 1: There are three corns in front, one is * * *, and how many cobs are there.
Health 2: When the bear didn't break the corn, there were three cobs in every four corns, and the bear broke 1, so the formula was 4× 3- 1 =.
Teacher: (Draw a horizontal line under 4×3) What does 4×3 want in the picture?
Health 2: How many corn cobs were there in the original four corn trees?
Teacher: Why should we reduce 1?
Health 2: The bear broke off one, so it was reduced by 1.
Teacher: There are multiplication, addition or subtraction in a formula. What should be counted first? Tell me about it.
Student: Add and subtract first.
Student: Calculate multiplication first.
Teacher: Please write and calculate first, and then communicate in groups to see which group of students can find the fastest and most accurate. (Student group activities. )
Teacher: Which group of students will report?
Health 1: When there are multiplication and addition, multiply first and then add. Let's take 3×3+2 as an example: calculate 3× 3 = 9 first, and then 9+1=1.
Health 2: When there are multiplication and subtraction, multiply first and then subtract. For example: 4× 3- 1, calculate 4× 3 = 12 first, then12-1=1.
Teacher: What a good speech! Do you have a conclusion in mind? What should be calculated first when encountering such equations as addition, subtraction, multiplication and division?
Student (Qi A): Multiply first, then add and subtract.
Through watching, talking, group communication and other activities, guide students to explore independently and cultivate the awareness of cooperation and communication; Let students fully express their personal views and respect their individuality.
Experienced the idea of diversification of problem-solving strategies and algorithms. )
Third, activity experience, entertaining.
Exercise 1: Pick the cob.
(The picture returns to the theme map)
(Animation show, while the teacher explains: Bear is carrying 1 corn cob, and walking back with brisk steps. Hey, there are many good friends ahead, including birds, dinosaurs, frogs and other small animals. These good friends see that the corn planted by Little Bear is so strong and delicious, and they all hope that Little Bear can feed it for himself. The bear thought for a moment and said, "I will give the corn on the cob to whoever can answer my question correctly." Students, do you want to try? (Student A: Yes! ) Yes, the teacher gave you 1 a small corn cob. )
(Pictured: The bear broke off again 1 root corn cob. )
Teacher: How many cobs are left now? Who can help bear calculate multiplication, addition and subtraction?
After thinking for a moment, the students raised their hands.
Sheng 1: Xiao Xiong * * * broke off two corn cobs, and the formula should be: 3× 3+ 1 = 10. Teacher: How is this formula worked out?
Students 1: multiply by 3× 3 = 9, and then add 9+ 1 = 10.
Teacher: You are great! Bear's first corn cob is for you.
Health 2: I have the following formula: 3× 4-2 = 10, first calculate 3× 4 = 12, then calculate12 =10.
Teacher: Can you tell me why you reduced it by 2?
Health 2: It turned out to be four corn trees, each with three on it.
A corn cob freed the bear.
I lost two, so I'm going to subtract two.
Teacher: That's good! I also sent you 1 a corn cob.
At this time, everyone became active and wanted corn on the cob. )
Teacher: Well, there is a secret in the remaining 10 corn cob. If you can solve this secret, then this corn cob is yours.
When the teacher clicks on every corn cob in the courseware, a formula of multiplication and division, addition, multiplication and subtraction appears respectively. Students can choose a corn cob to answer. )
Exercise 2: Harvest Party
Teacher: Autumn is the harvest season. To celebrate the harvest, Bear invited everyone to a get-together. Look! What did they bring? They not only brought fruit, but also brought problems to everyone. Whoever can answer these questions correctly will get these fruits. Students who answer correctly will get a fruit card. )
(Click on the monkey and the pig, and the first question on page 56 and the fourth question on page 58 will appear respectively. )
1, page 56 of the book, do 1 problem (students finish it independently first, and then the teacher asks questions) Teacher: How do you arrange it?
Health 1: 3× 4+2
Teacher: Do you have any questions for him (student 1)? (Students raise their hands in succession)
Health 2: What do you think?
What is the result of 3: 3 × 4?
Health 4: Can you calculate by multiplication and subtraction?
2. Question 4 on page 58 of the book (report after students finish independently. )
Exercise 3: Visit the Forest Orchard
Teacher: Just now the animals invited us to taste delicious fruit, and now they invite us to visit the forest orchard. Do you want to go?
Health: Yes!
Teacher: (There are pictures in the courseware) Look, this is a corner of the orchard. There are not only delicious fruits, but also fresh air and beautiful scenery. Look, it attracts swallows and deer. Let's have a little competition, shall we?
Health: Good!
Rules of the game: Divide the class into two groups (banana group and orange group). One group asks questions and the other answers. Get a fruit card for each question and a fruit card for each method. The two groups are interchanged. Finally, the team that gets the most cards will win the prize.
Exercise 4: Little Designer
Teacher: Just now, the small animals brought us many math problems. Can you design math problems? Please spread your imagination and design a problem of multiplication, addition and subtraction by placing learning tools or drawing pictures.
After the students design the questions, the deskmates appreciate each other and answer each other. )
Combine theme pictures with students' real life, create mathematical problems, further cultivate students' good study habits such as careful observation and independent thinking, and cultivate students' ability to find, ask and solve problems. )
Fourth, the whole class summarizes and shares the gains.
Teacher: Do you like this class today? What did you learn from this course? Please leave your seat, find your good friend and share the gains of this class with your good friend.
blackboard-writing design
Teaching reflection