First, multiplication

1, multiplication formula: factor x factor = product; Product factor = factor. Division formula: dividend-divisor = quotient; Quotient x divisor = dividend; Dividend quotient = divisor. Multiplication and division algorithm: when operating at the same level, it is calculated from left to right in turn; Two-stage operation, first multiply and then divide, then add and subtract.

2. When there are brackets, count the inside of brackets first, and then count the outside of brackets; When there are multiple brackets, count the brackets first, then the brackets inside, then the braces inside, and finally the brackets outside. Multiplication is a shortcut to add up the same numbers. The result of its operation is called product, and "X" is the symbol of multiplication.

3. The multiplication of integers (including negative numbers), rational numbers (fractions) and real numbers is a systematic summary of this basic definition. Multiplication can also be seen as calculating the objects arranged in a rectangle (integer) or finding the area of a rectangle with a given side length. The area of the rectangle does not depend on which side is measured first, which shows the exchange property.

4. The product of two measures is a new type of measure, for example, multiplying the length of two sides of a rectangle to get its area, which is the theme of size analysis.

Second, division.

1 and division are one of the four operations. Given the product of two factors and a non-zero factor, the operation of finding another factor is called division. Division of two numbers is also called the ratio of two numbers.

2. If ab=c(b≠0), the operation of finding another factor A by multiplying the product C and the factor B is division, which is marked as c÷b, pronounced as C divided by B, or B divided by C .. where C is called dividend, B is called divisor, and the result of A operation is called quotient.

Third, the formula

1. In mathematics, expressions refer to expressions listed when calculating numbers (or algebraic expressions), including numbers (or letters instead of numbers) and operation symbols (four operations, powers, roots, factorials, permutations and combinations, etc. ). According to the different calculation methods, the formulas are generally divided into horizontal and vertical.

2. Unlike expressions, expressions are expressions that connect data of the same type (such as constants, variables, functions, etc.). ) Use operation symbols according to certain rules. Expressions are expressions that connect numbers through operation symbols to calculate results, and need an equal sign.