For example, 8x2 16, check calculation 16÷8 ÷ 2, 16 ÷ 228, according to the multiplication law, the position and product of the exchange factor remain unchanged, and you can also use the position of the exchange factor for check calculation, for example, 4x5 ÷ 20, check calculation: 5x4 ÷ 20.
The fourth grade mathematics multiplication checking calculation is to divide the product obtained by multiplying two numbers by the multiplier. If the quotient obtained is equal to the multiplicand, then which product obtained by multiplying two numbers is correct; If the quotient obtained is not equal to the multiplicand, then the product obtained by multiplying two numbers is wrong.
Brief introduction of multiplication check calculation;
The so-called multiplication means that the multiplier multiplied by the multiplier equals the product, so the calculation of multiplication should be reversed, and the quotient obtained by dividing the product by the multiplier must be another divisor.
So when checking, the product in the original multiplication actually became the dividend, one of the multipliers became the divisor and the other divisor became the quotient. If the quotient it divides is not a number with a corresponding multiplier, then the multiplication problem may be wrong, or the division is wrong.
The formula of multiplication is that one factor multiplied by another factor equals a product. If you need to check, you can divide one factor by another, or divide the product by another factor, which is equal to one factor. You can also use the multiplication exchange law to exchange the positions of two factors for verification.