Phép chia hết và phép chia có dư - Toán lớp 3 - Cô Nguyễn Thị Điềm (DỄ HIỂU NHẤT)

Hello, students of Viet Duc. Today, you and I will accompany each other in the 3rd grade math and in the lesson on how to divide and how to divide. I invite you to observe on the board. I have 8 dots and I divide these 8 dots into 2 equal parts and to show you how to divide. I have 8 divided by 2. So 8 divided by 2, we have each part is 4 dots. 8 divided by 2 is equal to 4. 4 times 2 is equal to 8 times 8. And 8 divided by 8 is equal to 0. So in this division, we have 4. I repeat, 8 divided by 2 is equal to 4. 4 times 2 is equal to 8. 8 divided by 8 is equal to 0. And in this division, we see that when we divide evenly, we will not have any dots left. We say 8 divided by 2 is equal to divide all. And we can write 8 divided by 2 is equal to 4. And we will read 8 divided by 2 is equal to 4. We will go to the next example. She has 9 dots and she also divides these 9 dots into 2 parts. But do we see that these 2 parts are the same? Ah, not the same, but we will see the dots. And she demonstrates this division method. 9 divided by 2. And we will calculate this division method for her. 9 divided by 2. And in the division method, we do not see the division method 9 divided by 2. Therefore, we have to multiply this division method. And she multiplies 4. Because 4 times 2 is equal to 8, close to the number of divisions is 9. She has 4 times 2 is equal to 8. She writes 8. And she has 9 divided by 8 is equal to 1. It is correct with the previous division method, right? Ah, right, 1 dot. So we will repeat this division method. 9 divided by 2 is equal to 4. Write 4. 4 times 2 is equal to 8. 9 divided by 8 is equal to 1. And we say the division method 9 divided by 2 is the division method with 1 and the number of divisions here is 1. 1 is the number of dots, guys. And we can write the division method 9 divided by 2 is equal to 4. And the dot 1 is in the column. We read 9 divided by 2 is equal to 4, dot 1. And she also noticed that in the division method, the number of dots is always right. The number of dots will be smaller than the number of divisions, guys. This is the number of dots and this is the number of divisions. 1 is smaller than 2. So our division method is correct, guys. When the number of dots is larger than the number of divisions, we need to do the division method again. So when we see that the number of dots is smaller than the number of divisions, we can't do the division method anymore. Then we stop, guys. We pay attention to her, the number of dots is always smaller than the number of divisions. Just now, she and you have done 2 division methods together. That is the division method and the division method with dots. And in the division method, the number of dots is always 0. And in the division method with dots, the number of dots will be smaller than the number of divisions. Now, let's do some exercises. Exercise 1 requires us to calculate and write according to the model. Let's observe the model. 12 divided by 6. And in the model, 12 divided by 6 is 2. 2 times 6 is 12. Write 12. 12 minus 12 is 0. We write horizontally. 12 divided by 6 is 2. Now, let's do the next calculation. 15 divided by 3. She has 15 divided by 3 is 5. 5 times 3 is 15. Write 15. Straight line with the number 15 above, guys. Horizontally and 15 minus 15 is 0. She writes horizontally. Write with the letter above. Write 15 divided by 3 is 5. We just need to write the calculation horizontally. Now, let's move on to the next calculation. 20 divided by 5. And in the division method, we already know that 20 divided by 5 is 4. Write 4. 4 times 5 is 20. Write 20. 20 will be straight with the number 20 above. 20 minus 20 is 0. We write the calculation horizontally. Write. We just need to change it to horizontally. 20 divided by 5 is 4. And in the last calculation, there are 24 divided by 4. And 24 divided by 4 is 6. We have already learned how to divide 4. 6 times 4 is 24. Write 24 straight with the number 24 above. And 24 minus 24 is 0. So, we have found the result. We write it again, guys. Horizontally is fine. Write. 24 divided by 4 is 6. So, you and I have just done the first lesson. And you guys help me in the first lesson. In the first lesson, we will have a negative number here. Ah, there is a negative number. So, these equations are all division equations. Part b. We observe this example. 17 divided by 5. Start doing 17 divided by 5. Because 17 can't divide 5, so we will calculate the amount of damage. So that when the number of damage is divided, it will be close to the number of divisions. And here the amount of damage is 3. 3 times 5 is 15. Write 15. 17 minus 15 is 2. So, we have a negative number which is 2. And this negative number is smaller than the number of divisions. Ah, that's right. Negative 2 is smaller than 5. So, we have done it correctly. Now, we write it again horizontally. 17 divided by 5 is 3. And negative 2 is 0. Now, you and I will do the next division. 29 divided by 6. 29 can't divide 6. So, we will calculate the amount of damage. So that when the number of damage is divided, it will be close to the number of divisions. And here the amount of damage is 4. You will be wrong. 4 times 6 is 24. 24 is close to 29. If we calculate the amount of damage is 5, we will be wrong. 5 times 6 is 30. And here the number of divisions is 29. So, it is not correct. We can only calculate the amount of damage is 4. 4 times 6 is 24. She wrote 24. And here we have 29 divided by 24. So, 9 divided by 4 is 5. So, the number of divisions 5 is smaller than the number of divisions 6. We will write it horizontally. Write 29 divided by 6 is 4. Remember to write horizontally below 5. Now, let's move on to the next calculation. 19 divided by 3. And in the division table, there is no 19 divided by 3. So, we will calculate the amount of damage again. She will calculate the amount of damage here is 6. She is wrong. 6 times 3 is 18. 18 will be close to the number of divisions is 9. She will do it right away. 6 times 3 is 18. She wrote 18. 19 divided by 18 is 1. So, the number of divisions is 1. It is smaller than the number of divisions 3. She wrote the method of dividing horizontally. Remember to write the number of divisions. The number of divisions is 1. We will do the last method. 19 divided by 4. And here we also need to calculate the amount of divisions. When we remember the division table 4, we can easily calculate the amount of damage here. We will calculate the amount of damage as 4. Because 4 times 4 is 16. It is close to the number of divisions. But can we calculate the amount of damage as 5? When we calculate the amount of damage as 5, there is 5 times 4 is 20. So, the number of divisions is 19. We can't. So, we just calculate the amount of damage as 4. 4 times 4 is 16. She wrote 16. 19 divided by 16 is 9. 9 divided by 6 is 3. So, the number of divisions is 3. It is smaller than the number of divisions 4. So, our method of dividing cannot be divided. We write the method of dividing horizontally. 19 divided by 4 is 3. So, you and I have just done 4 methods of dividing. And these 4 methods of dividing are the methods of dividing with brackets. Let's start with question B. Question B. The first equation. 20 divided by 3. We will have 20 divided by 3 and the amount of damage is reduced. Ah, we enter it in the head. She entered 6 times 3 is 18. It is close to the number of divisions 20. She wrote 20. She entered 6 times 3 is 18. She wrote 18. So, she has 20 divided by 18. She wrote 0, 0 divided by 8. 20 divided by 18 is 2. So, she has the number of divisions 2. It is smaller than the number of divisions 3. She wrote the method of dividing horizontally. 20 divided by 3 is 6. Do you remember? When there is an odd number, we have to write the even number next to it. Next method of dividing. 46 divided by 5. And she remembered in the equation of dividing 5. She has 9 times 5 is 45. It is close to the number 46. She will have 9 times 5 is 45. She wrote 45. 46 divided by 5 is 1. So, she has the number of divisions 1. We write the method of dividing horizontally. Do you remember? Write the number of divisions next to it. It is close to the number of divisions 2. We go to the next method. She has 26, 28 divided by 4. We ask her to see 28 divided by 4. In the equation of dividing 4, what is the result? It is 7. She wrote 7. 7 divided by 4 is 28. 28 divided by 28 is 0. So, here the number of divisions is 0. What method of dividing is this? This is the method of dividing all. We write the method of dividing horizontally. 28 divided by 4 is 7. This is the method of dividing all. We don't need to write the number of divisions. Next, the equation of dividing 42 divided by 6. What is the result? 42 divided by 6 is 7. 7 divided by 6 is 42. She wrote 42. 42 divided by 42 is 0. This is also the method of dividing all. We write the method of dividing horizontally. So, in this part, we have calculated and done the methods of dividing. In it, there is also the method of dividing horizontally and the method of dividing all. Let's move on to the second exercise. In the second exercise, we will write right or wrong in the blank. Let's see the method of dividing 32 divided by 4. The result is 8. 8 divided by 4 is 32. 32 divided by 32 is 0. So, in this equation, we have done it correctly. Let me fill in for her. This is correct. The next equation is 30 divided by 6. And there is usually 4. 4 divided by 6 is 24. Write 24. 30 divided by 24 is 6. But let's take a closer look at the equation of dividing 6. How about the number of divisions? Ah, by the number of divisions. So, have you done it correctly? Ah, in this sentence, the method of dividing is wrong. So, I will fill in the letter S in the blank for her. And she asked me to do the method of dividing again for her. She will calculate 30 divided by 6. We will remember to help her in the equation of dividing 6. 30 divided by 6 is 5. 5 divided by 6 is 30. Write 30. And 30 divided by 30 is 0. So, in this equation of dividing, we have done it correctly. Let's continue with the equation of dividing C. 48 divided by 6 is 8. 8 divided by 6 is 48. Write 48. 48 divided by 48 is 0. We have done it correctly. Have you done it correctly? Ah, correct. We fill in D for her. The last equation. 20 divided by 3. Here, you write the result as 5. 5 divided by 3 is 15. Write 15. 20 divided by 15 is 5. Let's take a closer look at the equation of dividing. How about the number of divisions? Ah, the number of divisions is greater than the number of divisions. So, have you done it correctly? Ah, in this equation of dividing, we have done it wrong. So, we fill in S for her. Let's revise this equation. Equation 20 divided by 3. We remember the equation of dividing to help her. 20 divided by 3, what is the result? Ah, in the equation of dividing, there is no 20 divided by 3. So, we write the number of divisions. 20 divided by 3, she sees the result is 6. 6 divided by 3 is 18. It is close to the number 21. So, she will fill in 6. 6 divided by 3 is 18. She writes 18. 20 divided by 18 is 2. So, in this equation of dividing, there is a divisor. And the number of divisors is 2. The number of divisors is smaller than the number of divisors. Have you done it correctly? Ah, that's right. So, in the second lesson, we have learned and revised the equations that you did wrong. And we see that there are divisors, and there are divisors, too. Let's go to the third lesson. In the third lesson, we have calculated the small a part. Let's go to your homework. The small a part. 24 divided by 6. We have learned that in the equation of dividing, 24 divided by 6 is 4. 4 multiplied by 6 is 24. So, we write 24. And 24 divided by 24 is 0. Let's rewrite the equation in the horizontal form. And this is the division formula, so we don't need to write the divisors. The next equation is 31 divided by 5. Let's see if there is 31 divided by 5 in the equation of dividing. Ah, there isn't. But I remember that there is an equation 30 divided by 5 is 6. So, I will write 6. 6 multiplied by 5 is 30. Write 30. 31 divided by 30 is 1. Let's write the equation in the horizontal form. We remember that in the equation of dividing, we write the divisor next to it. Here is 1. The next equation is 41 divided by 6. I remember that in the equation of dividing, there is 41 divided by 6, right? Ah, there isn't 41 divided by 6, but we can calculate 41 divided by 6. 42 divided by 6 is 7. But we only have 41 here. So, we can't get 7. We will get 6 minus 7. And we have 6 multiplied by 6 is 36. So, 41 divided by 36 is 5. We have the divisor 5. I will write it in the horizontal form. And remember to write the divisor next to it. Here is the divisor 5. So, we have just finished part A. Now, let's move on to part B. Let's move on to part B. The first equation is 27 divided by 4. And we calculate the division here. 27 divided by 4 is 6. 6 multiplied by 4 is 24. 27 minus 24 is 3. And we have the divisor 3, which is smaller than the divisor 4. Let's write it in the horizontal form. 27 divided by 4 is 6. And we have the divisor 3. Let's move on to the next equation. 20 divided by 5. Is 20 divided by 5 in the divisor 5 table? That's right. We have 20 divided by 5 is 4. 4 multiplied by 5 is 20. So, this is the divisor 5. And we write it in the horizontal form. The last equation is 29 divided by 3. Let's see if there is 29 divided by 3 in the divisor 3 table. Ah, there is no 29 divided by 3, but there is the equation 27 divided by 3. 27 divided by 3 is 9. So, the answer is 9. 9 multiplied by 3 is 27. 29 minus 27 is 2. And this is also a divisor with a divisor. And the divisor is 2. Remember to write the divisor next to it. So, through lesson 3, we have calculated and calculated the divisors. There are divisors and divisors with divisors. So, through today's lesson, we have learned what is a divisor and what is a divisor with a divisor. And when we divide, we will see that the divisor is 0. It means that the divisor is 0. And the divisor with a divisor, we remember to remember that the divisor must always be less than the divisor. Goodbye everyone!