The concept of multiplication and division of rational numbers in the first year of mathematics of people's Education Press In urgent need of brothers and sisters
Rational number is: integer fractional decimal [including negative number, excluding infinite circular decimal] multiplication rule: multiply two numbers, get positive with the same sign, get negative with different sign, and multiply absolute value, multiply any number with 0, get 0 division rule: divide two numbers, get positive with the same sign, get negative with different sign, and divide absolute value, divide 0 by any number that is not equal to 0, get 0.0 divided by a number that is not 0, It is equal to the reciprocal of this number, 0 cannot be divisor