[ TOÁN 5 ] VIẾT SỐ TỰ NHIÊN TỪ NHỮNG SỐ CHO TRƯỚC _ CÔ NGUYỄN THỊ MAI QUỲNH _ HOCMAI

Topic 2: We will practice together on the structure of natural numbers as well as expand various types of problems related to this topic And the first exercise in topic 2 the teacher will introduce to you the type of problem of writing natural numbers from given numbers You have encountered some types of questions before but they are not clearly categorized by subject Then in this 4th grade review program the teacher will take you to a topic that is more specific and clear Look here I will show you the first thing some notes when you write natural numbers from the given numbers The first note is that to write the smallest natural number from the given numbers we need these conditions First if it's supposed to be the smallest natural number it has to be the natural number with the least number of digits possible Right And the second issue which is the priority behind After this first one Once we have determined the number of digits in the natural number you must prioritize placing the smallest digit in the highest place value But it has to be satisfied Is that the highest level of ours that will have to be different Right That's how we will arrange the numbers in the remaining rows in what order In ascending order Remember Remember these three priorities when you want to write the smallest natural number from the given numbers or satisfy the given conditions For example to demonstrate the smallest natural number from the given numbers Miss Minh gave a small example as follows She gives the natural numbers 0 1 2 3 and asks us to write the smallest natural number with three different digits Okay guys from these four digits there are many ways to write a three-digit natural number with different digits But we note that this is the smallest natural number The smallest is first we prioritize the number with the fewest digits possible To meet the requirement of having three digits we will enter one of the three getLength The smallest numbers in these three digits are 0 1 and 2 right So we remove the number 3 We can choose the numbers 0 1 and 2 Then we will sort these numbers 0 1 2 The smallest digit should be in the highest place so shouldn't zero come first Oh that's not correct Zero cannot be the first digit in natural numbers can it If zero is at the beginning now we will become a two-digit natural number no longer a three-digit number So we prioritize the smallest number that satisfies to be first as number 1 Then the remaining numbers must increase Between 0 and 2 0 is smaller and we arrange them increasing order So the answer would have to be number 100 102 right Number 102 satisfies that it is the smallest natural number There are 3 different digits formed from the numbers 0 1 2 and 3 On the contrary To write the largest natural number from the given numbers the conditions for it will be reversed First priority is that the number of digits must be as many as possible Is that clear As many as possible As per the problem's requirement For example if the problem asks to write a three-digit natural number we are only allowed to take three digits The second priority is that the largest digit is placed in the highest position Prioritize number 3 which is to arrange the digits in the remaining rows in descending order A similar example to the previous one is having four digits 0 1 2 3 Write the largest possible natural number with three different digits Different digits as large as possible We are ranked here This one we can't count the number of digits Why Because when considering the number of digits the problem already specified that there are 3 digits These 3 digits are the largest natural number So we will take the numbers 1 2 3 and remove 0 as the smallest number Then we will sort in this priority order Ah the largest digit in the highest place In these three numbers number 3 is the largest Therefore number 3 will be in the highest place which is the hundreds place The numbers are arranged in descending order Therefore the number 2 will come before the number 1 You got the result The number to write is 321 Okay Then after these notes our teacher and student will move on to part 2 which is the example exercise We will apply theories we have learned so far about natural numbers in the example exercise So that we can complete it This exercise gives the numbers 2 3 4 and 8 Write all the three-digit numbers with distinct digits from the four digits above Okay Oh when writing like this the children should avoid messy arrangements Because when we arrange things messily it's very easy to miss something So you will work with her in the following order The three-digit natural numbers formed from the digits 2 3 and 4 are Now she will prioritize arranging like this Since they are different numbers she prioritizes writing 2 3 4 and 8 Now we will place the number 2 in the hundreds place Because this is a three-digit number We have the following options if 2 is in the hundreds place That is you choose 3 in the tens place Then we have 234 Because they have to be different Or number 238 After arranging the number 3 in the tens place We continue to take 2 in the hundreds place but up to 4 in the tens place Then we have 243 248 Remember to follow the order Oh number 2 is still being selected in hundreds Then the next number we can arrange in the tens place is 8 So we have 283 or 284 Has the 2 in the hundreds place run out yet kids 2 in the hundreds place 3 in the tens place 4 in the tens place and 8 in the tens place There When selecting a number in the hundreds place the remaining three numbers will follow in the order they appear in the tens place Okay Then after the second number is completed in the hundreds place Then you will arrange the third number in the hundreds place The third digit in the hundreds place you will prioritize this digit 2 in the tens place Then she has 324 or the number 328 End the second number in the tens place We will move to the tens place of number 4 There are 342 or 348 The next number is 3 in the hundreds place but 8 in the tens place So it's 382 or 384 Are you ready Then now we will arrange this Number 4 in the hundreds place Number 4 in the hundreds place the number 2 in the tens place first Then she has 423 or 428 Then later 432 or 438 482 or 483 Then the fourth position was gone The fourth is hundreds Then the full numbers 2 tens 3 tens and 8 tens Now we will move to the number 8 in the hundreds place Then she has 823 824 Then 832 834 Are you ready 840 843 And how many numbers will we have in total Please observe this again for析 2 4 6 8 10 12 14 16 18 20 22 24 Is 24 numbers correct Because each 1 number in the hundreds place will give us 6 digits There are 6 natural numbers with 3 different digits And are they formed from the numbers 2 3 4 8 The second assignment the teacher gave the students is to use the six digits 0 3 5 1 6 and 9 Children write down the largest and smallest natural numbers Having all six digits present And of course the numbers will not be repeated Numbers cannot be repeated in them either Now let's recall the original theory that the teacher presented to you When writing the largest natural number from the given numbers we prioritize the number with the most digits And in this problem we have to write all six digits The second priority is that you will arrange the largest digit in the highest place Yes You will do them one by one according to the priorities First of all the largest number that can be written is Alright now we will prioritize this The largest number has the largest digit in the highest place So number 9 will be in the highest position Then we will sort them in descending order of the numbers right Now in the 4 numbers in the remaining 5 numbers the number 6 will be the second largest right Then comes 5 3 1 and 0 The largest number we can write is 965 310 What is the smallest number that can be written We must prioritize arranging them in the following order: the smallest number possible It is the number with the fewest digits possible In this case we still have to take six digits right But we will arrange them so that the smallest number is at the highest place So zero or one Oh we will have to choose one So that our six-digit natural number has meaning right So the number 1 Then arrange the numbers in ascending order That's 0 then 3 then 5 then 6 and then 9 She was given the smallest number that could be written which is 103 569 Exercise number 3 we will write the number from question A The largest number with 6 digits The problem does not require the children to write the largest 6-digit number with the same or different digits So we will write the same numbers which will satisfy right Now the largest number with 6 digits you see it is Number 9 is the largest single-digit natural number We will arrange it so that there are six 9s There since the problem does not require them to be different this will be the largest 6-digit number This number is read as 999 999 Write the smallest 5-digit number with all different digits The smallest 5-digit number So our first priority is to place the number 1 at the beginning After the number 1 we will write the number 0 Because this requires different numbers Then the 0 and the 1 must not be picked up again Then you will have the next number which is number 2 number 3 and number 4 The smallest number with 5 different digits is 10234 The largest number with 6 digits where the hundreds place is 2 But the problem does not require us to write different numbers So she will write the number 999 999 Hundreds is 2 she replaces it with the number 2 There she will get 999 999 The smallest number with six odd digits Oh the smallest number with six odd digits But the problem does not require the digits to be different Then she has the smallest six-digit number with all odd digits which is 111 111 There this is the six-digit number And the smallest one is odd The rest of you who used the numbers 3 5 and 7 are all larger than the number the teacher gave Okay Alright we'll now move on to Lesson 4 In Exercise 4 you will write the largest and smallest natural numbers for the teacher There are different digits such that the sum of the digits of the natural number equals 12 For this problem we will apply the noted information of theoretical part she taught the children That is wanting to write the largest natural number we will proceed according to 3 priorities And the priorities must be carried out in the correct order So now we will make a draft To see how the number 12 is broken down into the sum of a sequence of numbers Write down those number sequences Then we will arrange it to get the largest number Oh the first priority is to make it the largest natural number To write the largest natural number you must use numbers in a way that our natural number has the most digits The most digits en the number 12 the number 12 you will have to separate so that it becomes the sum of a sequence of numbers but all the numbers in it are the smallest the smallest to get to 12 right The smallest one she initially used the number 0 But the number 0 can only be used once Then comes the number 1 the number 1 then the number 2 add 3 Which in this case she has 0 plus 1 plus 2 plus 3 equals 6 this addition if added with 4 en she gets 10 10 needs to be added with 2 to make the total 12 but then the number 2 is repeated here So in this case she has to eliminate it right Then what about the next case the next case is that she will Add it to 5 if you add 5 then here she gets 6 plus 5 equals 11 you need to add 1 more to make the total 12 But this number 1 is the same as number 1 here the digits are not different so in this case she also eliminates it She goes Right Then now she will add 6 more Add 6 and then add 6 she will 0 plus 1 plus 2 equals 3 plus 6 which is 9 so the teacher will get 9 The largest natural number is 0 1 2 3 and 6 Okay Now we will arrange for her the order of these natural numbers Arranging them in order of priority is the larger number ghest in the top row number 6 in the top row then 3 2 1 and 0 Okay Then you will Fill in the answer for her on this side Okay Here's how we'll reason 12 is equal to 0 plus 1 plus 2 plus 3 and plus 6 Is that right Should be the largest natural number It can be writte what number is this 63 210 Are we done Then we have the solution for the largest number Now we will do the same to get the smallest number To be the smallest number it must be written with the fewest digits That is the top priority The fewest digits will allow you to separate them Twelve becomes a total of natural numbers that are greater than the digits Right Then twelve can be split into nine plus three Or what 8 plus 4 How much more 7 plus 5 6 plus 6 That 's it and so o But to write the smallest number we will choose case 3 and 9 She will get the number 39 Then she also argues here because 12 is equal to 9 plus 3 so atural number should natural number smallest can write can write It is number 39 Well have you understood the rules yet We will have to follow the correct priority order Then we can get the correct answer for you kids Problem 5 we have the question as a four-digit number 3 4 5 and 0 Write all even numbers with three different digits Note this The number must be even An even number means its units digit is 4 or 0 It has three digits and there are 3 digits so the first digit cannot be zero and these digits must be different Then we will arrange the numbers in descending order the first thing is we will have to write down all the even numbers There are 3 different digits from 3 4 5 and 0 have Is that right To write these numbers she would have to choose as follows umbers that can be writte These even numbers have 3 digits differe ca writte ow we will choose 0 as the units place 0 as the units place we will do it first then 3 as the hundreds place 4 is tens place 0 is ones place 3 continues as hundreds place 0 is ones place then we are left with the number 5 Okay After having the number 3 for hundreds then the number 3 for hundreds is over Then we have number 4 as hundreds 4 represents hundreds 3 represents tens 5 represents tens is that right Next is number 5 which opens hundreds 5 opens hundreds 4 opens tens or 5 opens hundreds 3 in tens 0 remains in units 0 in units So can the children write more We only have the choice of 3 4 and 5 respectively playing the role in the hundreds place Yes 3 hundreds 4 hundreds and 5 hundreds Now we will assign the number 4 to which place value Number 4 plays the role of the units place so we have 3 as the hundreds place making it 304 which is an even number 354 Are you ready Because the number 4 is in the units place the number 4 can no longer be chosen as the hundreds place the number 0 cannot be either If she chooses hundreds she can only choose number 5 for hundreds then she has 504 534 is that all It is an even number so we have 0 in the units place or 4 in the units place if not in the units place then choose If 4 is in the units place then only the numbers 3 and 5 can be in the hundreds place So the numbers you can write include the 10 numbers listed on the following table right Now we will have to arrange these 10 numbers in descending order She will write the second one that is arranging order From large to small It's the largest one is definitely 5 in the hundreds place then she has 540 530 504 and 534 en we will arrange these numbers first the largest is 540 we write 540 first after 540 there is 534 Temporarily place the brick here please 534 write 534th then comes the 530 yet 530 then 504 umber 5 hundreds is the largest one then the next largest number will have number 4 in the hundreds place en here she has 430 and 450 then 450 is larger we sort first here 450 en comes 430 Here's 400 all the numbers I've used the teacher underlined them the rest 4 numbers There are 3 making hundreds so 354 is larger we arrange 354 first then 300 350 350 then uncover 340 and up to 304 this is one of the types of problems that is also very common during the process of students learning about natural numbers Then through today's lesson I hope the children have gained more new knowledge for the writing section on the structure of natural numbers right and wish you all good study hello and goodbye but remember that before the end of today's lesson Then don't forget your self-practice exercise dear students Bye bye