Law of addition and association: a+b+c=(a+b)+c=a+(b+c) three numbers are added, the first two numbers are added first, and then the third number is added, or the last two numbers are added first, and then the sum is unchanged. This is called the law of additive association.
The essence of subtraction: a-b-c=a-(b+c) One number subtracts two numbers continuously, and the sum of the last two numbers can subtract the first number, and the difference is unchanged. This is the essence of subtraction.
Multiplication commutative law: a×b=b×a is multiplied by two numbers, and the addend positions are interchanged, and the product is unchanged. This is called multiplicative commutative law.
Multiplication and association law: a×b×c=(a×b)×c=a×(b×c) multiply three numbers, first multiply the first two numbers and then multiply the third number, or multiply the last two numbers and then multiply the first number, and the product remains unchanged. This is called the law of multiplicative association.
Multiplication and distribution law: (a+b)×c=a×c+b×c Multiplies the sum of two numbers by the third number, which is equivalent to multiplying these two numbers by this number respectively, and then adding their products, and the products are unchanged. This is the so-called multiplication and distribution law.
Deviation property: a÷b÷c=a÷(b×c) A number divided by two numbers equals the product of a number divided by two numbers, and the quotient remains unchanged.