1. Master the arithmetic of addition, subtraction, multiplication and division of rational numbers.

2. Be able to flexibly use five algorithms (additive commutative law, addition law, association law; Multiplicative commutative law, multiplicative associative law, multiplicative additive distributive law)

3. Understand the order of mixed operations of rational numbers: advanced operations to low-level operations, operations at the same level from left to right, and from small to large when there are brackets.

Common inspection methods

The operation of rational number is the basis of mathematical operation. Through the analysis of various middle school mathematics examination questions, we can see that the key points of rational number operation are:

1. Investigate the confusing and error-prone related operations and the determination of symbols, such as the subtraction and multiplication of rational numbers.

2. Investigate the understanding and flexible application of various operational meanings and rules.

3. Combined with the problem situation in real life, the application of real number operation is investigated. The question type is generally a calculation problem.

Example (20 10 Harbin, Heilongjiang) The average temperature in Harbin 1 month in a certain year is-18℃, and the average temperature in March is 2℃, so the average temperature in March is higher than 1 month (? )

(A) 16℃ (B)20℃ (C)- 16℃？ (4). -20℃

Analysis option B.

Misunderstanding reminder

If you don't master the arithmetic of rational number subtraction, you must pay attention to that subtracting a number is equal to adding the inverse of this number, and the inverse of-18 is 18.