1. Understanding of large numbers

1). 10, the first digit on the left is a million digits, and the corresponding counting unit is "million", and 10 is one million digits.

2). The first digit on the left of the million digits is 10 million digits, and the corresponding counting unit is "10 million digits", and100000 digits is 10 million digits.

3). The first digit to the left of ten million digits is one hundred million digits, the corresponding counting unit is "one hundred million digits", and100 million is one hundred million digits.

4). 10 billion is one billion, 10 billion is ten billion, and 10 billion is one hundred billion.

★ Understanding of numbers within 100 million:

One hundred thousand:100000; One million:100000;

Ten million:100000; 1 100 million:1010 million;

2. The advance rate between counting units: one (one), ten, one hundred, one thousand, ten thousand, one hundred thousand, one million, ten million, one hundred million ... are all counting units, and the advance rate between every two adjacent counting units is 10.

3. Numeric, Graded and Decimal Numeric Sequence Table

1) digits: one (one), ten, hundred, thousand, ten thousand, one hundred thousand, one million, ten million, one hundred million ... are all counting units. Arrange these counting units in a certain order, with one number occupying one position. These positions are called numbers.

2) Series: every four digits from the right are one level.

Unit, ten, hundred and thousand are all levels;

Ten thousand digits, one hundred thousand digits, one million digits and ten million digits are ten thousand digits (four zeros after the number);

One billion, one billion, one billion, one billion is one billion (eight zeros after the number);

Mega (12 zeros after the number) ...

When grading, pay attention to grading from low position to high position.

3) Decimal number sequence table: The number sequence table consists of three parts: number level, number and counting unit.

Second, the census.

1. Pronunciation of large numbers

1) Grading first, then reading from a higher level, reading from one level to another;

2) How to read hundreds of millions: read hundreds of millions first, then tens of thousands, and finally read one level (that is, start from a high position). When reading numbers of 100 million or 10,000 levels, read them according to the reading method of each level, and add a word "100 million" or "10,000" after reading;

3) No matter how many zeros are at the end of each level, other digits have one or several zeros, and only one zero is read. (0 at the beginning or middle of the stage should be read, and 0 at the end of the stage should not be read. )

2. How to write large numbers

There are several levels of clear digital writing; Write down from a height, level by level; Write "0" on any number without a counting unit.

Third, the land area.

1.km2: the area of a square with a side length of 1km is 1km.

2. The comparative scale of more than 10,000:

1) The number of digits is different, and the number with more digits is larger.

2) The digits are the same. Compared with the high digits, the number of the highest digits is larger. If the numbers on the highest bit are the same, compare the numbers on the next bit in turn until the size is compared.

3. Rewrite the integers of 10,000 yuan and 100 million yuan into numbers with "10,000 yuan" or "100 million yuan" as the unit:

1) Rewrite an integer into a number with "ten thousand" as the unit: remove four zeros after ten thousand digits and add the word "ten thousand";

2) Rewrite the integer number into a number with "100 million" as the unit: remove the eight zeros after the hundred million digits and add the word "100 million".

Fourth, know the approximate figures.

1. Characteristics of exact numbers and approximate numbers

The approximate number is close to the exact number, preceded by the words "about" and "near". Function: easy to express and easy to remember.

2. Find the approximate figure by rounding.

If the number on the highest bit of the omitted part is less than 5, the mantissa will be completely rounded off (called "four homes"), and the corresponding unit or number of zeros will be added.

If the number of digits of the most significant bit of the omitted part is equal to or greater than 5, you need to enter 1 (called "quintuple") on the previous digit, then discard all digits and add the corresponding unit or the corresponding number of zeros.

18000≈20000, or 18000≈20000, where "≈" is pronounced as "about equal to".

Which place is accurate depends on the number of the next place. If the number in the next position is less than 5, use the four-shed method; If the next number is greater than 5, the decimal method is used. For example, accurate to 10 thousand digits, only a few thousand, accurate to 100 million digits, only tens of millions.