Summary of statistical knowledge points in the first volume of mathematics in the fourth grade of primary school
Planting garlic seedlings (1) (bar chart)
Knowledge points:
1 and 1 in the statistical chart represent different units, so it is necessary to judge how many units 1 represents according to the specific situation. The amount of data is large, and each 1 grid represents more units, while the amount of data is small, and each 1 grid represents fewer units.
2. Understand the meaning of the data on the bar chart.
3. Make clear the characteristics of the bar graph: intuitive, convenient and easy to check.
4. Bar chart making method: determine the horizontal direction and mark the items; Determine the number represented by the vertical direction (the number represented by one grid); Draw straight lines with different lengths according to the size of the data; Write the title.
Supplementary knowledge points: get a preliminary understanding of the composite bar chart, get information from it and answer the corresponding questions.
Planting garlic seedlings (2) (broken line statistical chart)
Knowledge points:
1, broken-line statistical chart: you can get the information of data changes and make simple predictions.
2. The method of broken-line statistical chart: on the grid paper, mark the points according to the given data, and then connect the points with lines in order.
3. Be able to see the information provided by the dotted statistical chart and answer related questions.
Supplementary knowledge points:
1. The difference between a bar chart and a line chart: a bar chart indicates the quantity with a straight line, and a line chart indicates the change of quantity with a broken line.
2. Have a preliminary understanding of the statistical chart of compound broken lines, from which we can get the corresponding information and answer the questions raised.
The arrangement of four operation knowledge points in the second volume of mathematics in the fourth grade of primary school
Law of addition:
1, where the two addends exchange positions and the sum remains unchanged, is called additive commutative law.
Alphabetic formula: a+b=b+a
2. Add the first two numbers, or add the last two numbers first, and the sum is unchanged. This is the so-called law of addition and association.
Alphabetic formula: (a+b) +c=a+(b+c)
(2) the law of multiplication:
1, exchange the positions of two factors, and the product remains the same. This is called multiplicative commutative law.
Alphabetic formula: a×b=b×a
2. Multiply the first two numbers, or multiply the last two numbers first, and the product remains unchanged. This is the so-called law of multiplication and association.
Letter formula: (a×b)×c=a×(b×c)
3. When the sum of two numbers is multiplied by a number, you can multiply it first and then add it. This is the so-called law of multiplication and division.
Use the letter formula: (a+b)×c=a×c+b×c or a× (b+c) = a× b+a× c.
Expansion: (a-b)×c=a×c-b×c or a× (b-c) = a× b-a× c.
(3) Simple subtraction operation:
1, a number subtracts two numbers continuously, and you can subtract the sum of these two numbers with this number.
Expressed in letters: a-b-c=a-(b+c)
2. One number subtracts two numbers continuously. You can use this number to subtract the last number and then subtract the previous number.
Expressed in letters: A-B A-B-C = A-C-B C-B.
(4) Simple division operation:
1, a number is continuously divided by two numbers, and this number can be divided by the product of these two numbers.
Expressed in letters: a÷b÷c=a÷(b×c)
2. A number is continuously divided by two numbers. You can divide this number by the last number, and then divide the previous number.
Expressed in letters: a \b \c = a \c \b
Summary of knowledge points in the first volume of fourth grade mathematics: count
Knowledge points:
Hundreds of millions of reading methods.
You must first read the numbers of 10, 1 0,000 and1100 million, then10,000, and finally 100. (that is, reading from a high position) Numbers of 100 million or 10,000 levels are all read by individual levels, followed by 100 million or 10,000. The zero at the end of the stage is not read, and the zero in the middle of the stage must be read. No matter how many zeros there are in the middle, read only one zero.
How to write numbers within 100 million.
Write from the top in numerical order. If there is no one in the middle or at the end, write 0 on that one.
Methods of comparing numbers.
Multi-digit comparison size, if the number of digits is different, then the number of digits is large and the number of digits is small. If the digits are the same, start with the first digit from the left, which number is larger and which number is larger. If the first digit from the left is the same, start to compare with the second digit … until the size comparison is finished.
Land area (multi-digit rewriting)
Knowledge points:
The method of rewriting numbers in units of "ten thousand" or "hundred million".
Taking "ten thousand" as the unit, the four zeros at the end must be removed and ten thousand words should be added; With "100 million" as the unit, the last eight zeros must be removed and hundreds of millions of words added.
The meaning of rewriting.
In order to facilitate reading and writing.
Forest area (approximate figure)
Knowledge points:
Characteristics of exact numbers and divisors.
The exact number is generally in the unit of "one", and the approximate number is in the unit of "ten thousand" or "one hundred million", and the mantissa is omitted.
The method of keeping approximate values by rounding.
Look at the next number to be reserved according to the requirements in the question. If this number exceeds 5, proceed to the previous number. If it is less than 5, give it up. Regardless of the last few digits of the mantissa. If it is accurate to 10 thousand digits, only a few thousand can be seen, and if it is accurate to 100 million digits, only tens of millions can be seen. Finally, be sure to write the name of the company.
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