Math 6 Chapter 1 Lesson 3: Write natural numbers số
1. Summary of theory Tóm
1.1. Numbers and digits
Form the concept of onedigit numbers, twodigit numbers, threedigit numbers,…
When writing natural numbers with five or more digits, people write each group of three digits from right to left separately for easy reading, for example: 12 345 678
Need to distinguish: Number with digits, number with tens digit, number with hundreds digit…
1.2. Decimal system
The way to write numbers as above is how to write numbers in the decimal system. In the decimal system, every ten units in an element make up one unit in the preceding row.
For example:
\(234=200+30+4\)
\(\overline {ab} = a.10 + b\left( {a \ne 0} \right)\)
1.3. Attention
In addition to the above ways, cpnf has other ways of writing numbers, such as Roman numerals.
Number 
I 
DRAW 
X 
Corresponding value in decimal system 
first 
5 
ten 
2. Illustrated exercise
Question 1: Write the smallest fourdigit natural number and write the largest threedigit natural number số
Solution guide:
The smallest fourdigit natural number is 1000 because \(\left( {a \ne 0} \right)\)
The largest threedigit natural number is 999 .
Verse 2: Write the smallest fivedigit natural number with twodigit differences and the largest twodigit natural number with twodigit differences.
Solution guide:
The smallest fivedigit natural number with a double difference is 10 234 .
The largest natural number that has two digits that are two different from each other is 98 .
Question 3: Given five digits 1; 0; 2; 5; 7
Write the largest fivedigit natural number that differs from them
Write the smallest fivedigit natural number that differs from that digit
Solution guide:
The largest fivedigit natural number that differs from those is: 75 210
The smallest fivedigit natural number that differs from those is: 10 257
3. Practice
3.1. Essay exercises
Question 1: Write the smallest threedigit natural number and the largest fourdigit natural number.
Verse 2: Write the smallest fourdigit natural number that is double one and the largest threedigit natural number that differs by one.
Question 3: Given five digits: 1; 3; 5; 7; 9
Write the largest fivedigit natural number that differs from those digits.
Write the smallest fivedigit natural number that differs from that digit.
3.2. Multiple choice exercises Bài
Question 1: The largest 3digit 5digit natural number is
A. 99999
B. 98765
C. 99000
D. 99990
Verse 2: The largest threedigit natural number is:
A. 999
B. 988
C. 989
D. 987
Question 3: Given a 4digit natural number 8753. Which of the following statements is false?
A. The tens digit is 5
B. The hundredth is 87
C. 8753 = 8000 + 700 + 50 +3
D. Is the largest 4digit natural number số
Question 4: The Roman numeral XXVIII corresponds to what value in the decimal system:
A. 27
B. 28
C. 29
D. 30
Question 5: Given three digits 0, 2, 4. How many 3digit natural numbers are there whose digits are different?
A. 2
B. 3
C. 4
D. 5
4. Conclusion
Through this lesson of Recording natural numbers, students need to complete some of the objectives given by the lesson, such as:

Form the concepts of onedigit numbers and twodigit numbers.

Get familiar with the decimal system.
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