Answer: There are two ways to check the vertical multiplication: (1) product ÷ one factor = another factor; (2) Apply the multiplication exchange law: exchange the positions of two factors and multiply again.

Here are some examples:

Knowledge expansion:

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.

Thirdly, multiplicative commutative law.

When two numbers are multiplied, the position of the exchange factor remains unchanged, and their products remain unchanged, which is called the multiplication exchange law. Use letters to represent a×b=bxa.