Multiplication law: multiplication commutative law: a×b = b×a multiplication associative law: a×b×c = a×(b×c) multiplication distributive law: a×c+b×c=c×(a+b) a×c-b×c=c×(a-b).
Nature of division: a÷b÷c = a÷(b×c).
Subtraction property: a–b–c = a-(b+c).
Law of solving equations: ◇ addend+addend = sum; Appendix = sum-another addend. ◇ minus-minus = difference; Subtraction = difference+subtraction; Subtraction = minuend-difference. Factor × factor = product; Factor = product ÷ another factor. Divider ÷ Divider = quotient; Dividend = quotient × divisor; Divider = dividend quotient.
Travel problem: distance = speed × time; Time = distance/speed; Speed = distance/time.
Decimal division:
1, fractional division has the same meaning as integer division. It is an operation to find the other factor by knowing the product of two factors and one of them.
For example, 2.4÷ 1.6 means that the product of two known factors is 2.4, and one factor is 1.6, so what is the other factor?
2. Divide the decimal by the integer and divide it by the integer. The decimal point of quotient should be aligned with the decimal point of dividend. If there is a remainder at the end of the division operation, add 0 to continue the division operation.
3. If the dividend is greater than the divisor, the quotient is greater than 1. If the dividend is less than the divisor, the quotient is less than 1.
4. Calculating the divisor is the division of decimals. First, move the decimal point of the divisor to make it an integer. Move the decimal point of the divisor to the right by several digits, and the decimal point of the dividend by several digits. If the number of digits is not enough, add 0 to make up. Then it is calculated by fractional division with the divisor being an integer.
5. When a number (except 0) is divided by 1, the quotient is equal to the original number.
When a number (except 0) is divided by a number greater than 1, the quotient is less than the original number.
When a number (except 0) is divided by a number less than 1, the quotient is greater than the original number.