2. Counting units: one tenth and one percent of one, ten, one hundred, one thousand, ten thousand ... .....

3. Comparison of integer sizes: To compare the sizes of two integers, first look at the number of digits. If the number of digits is different, the number with more digits will be larger; The digits are the same. Compared with the highest digit, the number in the same digit is larger.

4. Comparison size of decimals: look at the integer part first, and the bigger the integer part, the bigger it will be; And so on.

5. The comparative size of scores: the scores with the same true and false scores or the same integer part: the denominator is the same, and the numerator is large; The fraction with the same numerator and small denominator is large; Different denominators and numerators, and then compare them after sharing. Fractions with different integer parts: The larger the integer part, the greater the score.

6. Contrast between positive and negative numbers: positive numbers are greater than negative numbers. Negative numbers are compared with negative numbers. The larger the number after the negative sign, the smaller the negative number.

7. The relationship between the basic nature of fraction and decimal: The basic nature of decimal is a special case of fractional nature. For example: 0.3→10/30.30→100/30 0.300→1000/300.

8. If the decimal point moves one place to the right, the decimal point is expanded to 10 times, and the two digits are 100 times, and so on; If the decimal point moves one place to the left, the number will be reduced to 10 times, and if it moves two places, it will be 100 times. ......

9. Meaning of factors and multiples: It is known that A, B and C are positive integers (numbers do not include 0) and a×b=c, then C is a multiple of A and B, and A and B are factors of C, and multiples and factors are interdependent.

10, meaning of prime number: A number is called a prime number if it has only two factors: 1 and itself. The minimum prime number is 2, 2 is the only even prime number, and there is no maximum prime number. Meaning of composite number: A number is called a composite number if it has other factors besides 1 and itself. The smallest composite number is 4, and there is no largest composite number.