Significance of multiplication: It is a simple operation to find the sum of (several identical addends). The meaning of division is a simple operation to find the difference between several numbers. The relationship between the parts: factor × factor = product, one factor = product ÷ another factor. Dividend = quotient, divisor = dividend = quotient, dividend = quotient × divisor.
Multiplication and division 1. Integer multiplication rule: from the right, multiply the first factor by the number on each bit of the second factor, and the end of the number will be aligned with which bit of the second factor; Then add up the numbers multiplied by several times. (Multiply with 0 at the end of an integer: you can multiply the number before 0 first, then see how many zeros are at the end of each factor, and add a few zeros at the end of the multiplied number. )
Second, the law of decimal multiplication: calculate the product according to the law of integer multiplication; See how many decimal places there are in the factor, counting from the right of the number and pointing to the decimal point. There is a 0 at the end of the decimal part of the number, so it is generally necessary to remove the 0 and simplify it. The law of fractional multiplication: multiply the numerator of each fraction as the numerator, multiply the denominator of each fraction as the denominator, and then reduce the fraction.
Third, the division rule of integers: start from the high order of the dividend, first look at how many digits the dividend has, and then try to divide the first few digits of the dividend by the divisor. If it is smaller than the divisor, divide it by one digit as much as possible; Write the quotient on it except the dividend; The remainder after each division operation must be less than the divisor.
Fourth, the divisor is the decimal division rule of integer: according to the integer division rule, the decimal point of quotient should be aligned with the decimal point of dividend; If there is a remainder at the end of the dividend, fill in zero after the remainder and continue the division.
5. Decimal division rule that divisor is decimal: To calculate the division of divisor is decimal, first move the decimal point of divisor to make it an integer; The decimal point of the divisor is shifted to the right by several digits, and the decimal point of the dividend is also shifted to the right by several digits (the digits are not enough, and the end of the dividend is supplemented by "0"); Then it is calculated according to the division rule that the divisor is an integer.
Sixth, the division rule of fractions: the numerator of the dividend multiplied by the denominator of the divisor is the numerator; Multiply the denominator of the dividend by the numerator of the divisor as the denominator. (that is, the dividend is a constant, which is the reciprocal of multiplication and division)