Analysis: This topic examines the reading and writing of multiplication formulas, keeping in mind what can be done in class.

Multiplication is one of the four operations-"X" is the multiplication sign, the numbers before and after the multiplication sign are called factors, the factors are also called multipliers, "=" is the equal sign, and the numbers after the equal sign are called products. In the current textbooks, only "multiplication" is said, not "multiplication". Pay attention to the difference between division and division.

Multiplication algorithm:

1, multiplication commutation law:

Multiplicative commutative law is the multiplication of two numbers, the position of the exchange factor, and their products are unchanged.

a×b=b×a .

It is called the exchange method.

2, the law of multiplication and association:

Multiply three numbers, the first two numbers are multiplied and then multiplied, or the last two numbers are multiplied and then multiplied, and the product remains the same. The main formula is a×b×c=a×(b×c), which can change the operation order in multiplication. In daily life, the application of multiplicative associative law is not extensive, but mainly plays a simple role in some complex operations.

3, the law of multiplication and distribution:

The sum of two numbers multiplied by the same number is equivalent to two addends multiplied by this number respectively, and then the two products are added, and the sum is unchanged. The letter expression is: a× (b+c) = a× b+a× c.