First, the law of multiplication
The multiplication rule is: two numbers are multiplied, the same sign is positive, the different sign is negative, and the absolute value is multiplied. 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. From the philosophical point of view, multiplication is the result of qualitative change caused by additive quantity.
The multiplication rule of one digit. The product of two one-digit numbers can be calculated by addition according to the definition of multiplication. Usually, the product of any two one-digit numbers can be directly obtained by using the multiplication table. Multi-digit multiplication rule. Multiply the number on each bit of the multiplicand by the number on each bit of the multiplier in turn, and then add the products.
Second, the algorithm of multiplication
The position product invariance law and multiplication operation law of multiplication exchange factors, also known as multiplication properties, include exchange law, association law and distribution law. The application of these algorithms can simplify the calculation of some multiplication problems.
1, multiplication method of substitution and multiplication method of substitution are the multiplication of two numbers, and the positions of the exchange factors are unchanged. It is called the exchange method.
2, the law of multiplication and association, three numbers multiply, first multiply the first two numbers, and then multiply with another number, or multiply the last two numbers first, and then multiply with another number, the product is unchanged.
3, multiplication and division method, the sum (difference) of two numbers multiplied by the same number, you can first multiply the two addends (subtraction) by this number, and then add (subtraction) the two products, the product is unchanged.
Third, the method of learning mathematics well
1, mathematics should master the theory by doing problems.
Although there are many formulas and theorems in mathematics that students need to recite and memorize, they can't memorize them by rote. They need to learn mathematical thinking, clarify mathematical thinking and solve problems with mathematical thinking, so they can naturally master theoretical knowledge in the process of doing problems. Doing problems is a process of constantly consolidating knowledge and re-understanding mathematical theory. You can't know what won't happen unless you do the problem.
The way to learn math well is to do more problems.
Although this kind of problem-solving can be understood as problem-solving tactics, it is not the same as problem-solving tactics, because it is almost impossible to learn anything without doing problems in mathematics, and it is impossible to improve scores, but it is also harmful to blindly do more problems without reflecting and summarizing. The most taboo of mathematics is that it seems that you can do it, but you get stuck when you do it yourself.