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The Knowledge Structure of Number Represented by Letters in Unit 3 of Mathematics, Beijing Normal University, Seventh Edition
1) Quantity and calculation

How to read and write numbers within (1) billion?

Counting units are "one hundred thousand", "one million" and "ten million". Decimal relationship between adjacent counting units. Reading and writing methods within 100 million. Comparison of the size of numbers. About the number of tens of thousands.

(2) addition and subtraction.

Simple addition and subtraction algorithm close to integer ten and integer hundred.

The relationship between the parts in the addition and subtraction formula. Find the unknown number X.

(3) multiplication and division.

Changes in products. Invariance of quotient. Simple algorithm of adding 0 at the end of dividend and divisor.

A simple algorithm of multiplier approaching integer ten or integer hundred.

Multiply and divide the relationship between the parts in the formula to find the unknown X.

(4) Estimation of large numbers ①. Introduction of abacus or calculator.

(5) Elementary arithmetic.

Brackets. Formula problem of three-step calculation.

(6) Integer and its four operations and their operation rules.

Natural numbers and integers. Decimal symbol. Reading and writing.

The significance of four operations. The relationship between addition, subtraction, multiplication and division. Divisibility and division with remainder.

Operating rules. Simple operation.

(7) The meaning and nature of decimals. Addition and subtraction.

The meaning and essence of decimals. Comparison of decimal sizes. Decimal shift causes the change of decimal size. Approximation of decimals.

Addition and subtraction. The law of addition is extended to decimals.

(2) Quantity and measurement

Year, month and day. Flat year and leap year. Century. 24-hour timing method.

Measurement of angle.

Area unit.

(3) Preliminary knowledge of geometry.

Determination of straight line. Measure the distance (tool measurement, step measurement, visual inspection).

Ray. Right angle, acute angle, obtuse angle, right angle, * fillet ①. Vertical line Draw a vertical line. Parallel lines. Draw parallel lines.

The characteristics of a triangle. The sum of the internal angles of a triangle.

(d) Basic knowledge of statistics

Simple data collation. A preliminary understanding of simple statistical charts. The meaning of the average. Find a simple average.

(5) Application problems

Solve the application problem of two-step calculation. Solve the easy application problem of three-step calculation.

(vi) Practical activities

Organize activities related to the surrounding things. For example, during holidays, student groups organize an investigation activity. According to the budget, how much does each person have to pay for the activity?

Teaching requirements

1. Know the counting units "100,000", "million" and "ten million" and master the decimal counting method. You can read and write multiple numbers according to several levels. Know natural numbers and integers. According to the requirements, a number will be rounded off and the mantissa will be omitted, and a rough number will be written.

2. Can orally calculate the addition and subtraction of tens of thousands of integers. Add and subtract hundreds and dozens. Learn simple addition and subtraction algorithms close to integer ten and integer hundred, and be able to calculate flexibly. Master the relationship between the parts in the addition and subtraction formula, and find the unknown X according to this relationship.

3. Check the multiplier with the position of the exchange multiplier. Know the invariance of quotient. Multiplier and divisor are the multiplication and division of integer hundred. Learn some simple algorithms. Master the relationship between the parts in the multiplication and division formula, and find the unknown X according to this relationship.

4. Understand the meaning of the four operations and master the relationship between addition, subtraction, multiplication and division, so that students can be inspired by dialectical materialism. Algorithms can be applied to perform some simple operations. Four operations will be performed with parentheses.

5. Understand the meaning and nature of decimals. Proficient in decimal addition and subtraction (the limit of digits is the same as integer addition and subtraction) and simple oral calculation.

6. Know the time unit year, month and day, and know the number of days in normal year, leap year and every month. A 24-hour timer will be used to indicate the time.

7. Know the ray and angle, know the size of the angle, measure the angle with a protractor, and draw the angle according to the specified degree. Have a preliminary understanding of vertical lines and parallel lines, and can draw vertical lines, parallel lines, rectangles and squares with straightedge and triangular ruler. Master the characteristics of triangles. Know the sum of the angles inside the triangle.

8. Know the unit of land area (hectares, square kilometers). Learn to use measuring tools to measure straight lines and short distances on the ground.

9. Have a preliminary understanding of simple statistical charts. Understand the process of collecting and organizing data. Understand the meaning of average. You will find a simple average. Through statistical materials, students can understand the achievements of China's socialist construction.

10. It can solve the application problem of two-step calculation. It can solve the relatively easy application problem of three-step calculation.

1 1. Combine problem solving with calculation, and further cultivate students' habit of checking and checking, as well as a serious and responsible attitude.

12. Through practical activities, cultivate students' ability to find mathematical problems from surrounding situations and solve problems with what they have learned, and cultivate students' mathematical consciousness.