For example, addition needs subtraction and division needs multiplication. Calculate A+B = C, check C-B = A, and operate. Mathematically, operation is a behavior, and a new quantity is obtained through possible combinations of known quantities. The essence of operation is the mapping between sets.
The addition check calculation in primary school mathematics is to use the opposite method of addition and subtraction to check the calculation. For example, 12+24=36, then 36-24 can be used to calculate the result. If it is equal to 12, then the calculation is correct.
First, the calculation method of multiplication
There are two main checking methods for multiplication formulas:
Method 1: product, where one factor = another factor. It is based on the reciprocal relationship between multiplication and division.
Method 2: According to the intersection law of multiplication, check the positions of two factors in the exchange formula.
Second, the relationship between multiplication and division.
Division is the inverse of multiplication.
Factor × factor = product, one factor = product ÷ another factor; ?
Dividend = quotient, divisor = dividend = quotient,? Dividend = quotient × divisor;
Know the product of two factors and one of them, find the other factor and divide it.