3 1x27、53x32、57x4 1、22x79、50x67、92x37、43x82、 164、63x72、2 1x58、22x80、24x35、 19x66、30x54、79x20、83x43、7 1x67

First, multiplication skills:

1, multiplicative commutative law: a * b = b * a

2. Multiplicative associative law: a*b*c=(a*b)*c=a*(b*c)

3. Multiplication distribution law: (a+b) * c = a * c+b * c; (a-b)*c=a*c-b*c

Two, vertical calculation multiplication should pay attention to four issues:

1, the last digit of two numbers should be aligned.

2. Write as many numbers as possible above, and write as few numbers as possible below to reduce the times of multiplication.

3. If there is a "0" at the end of both numbers, the last digit of the number can only be aligned before the "0" when writing vertically, and finally the number "0" owned by the two numbers after vertical product is added.

4. Decimal multiplication should determine the position of the decimal point of the product according to the multiple of the decimal.

Extended data:

Each letter in the multiplication formula can generally represent a number, a single item, a polynomial, and some can also be extended to fractions and roots. Multiplication formula is an important content of algebraic expression multiplication. Mastering the multiplication formula accurately and skillfully is of great significance for learning the multiplication of algebraic expressions and even other operations of algebraic expressions. Multiplication formula is the most commonly used and basic formula, from which other formulas can be derived.

The square of a polynomial is equal to the sum of the squares of the terms, plus twice the product of every two terms. Most formulas can be used not only smoothly (polynomial multiplication) but also reversibly (factorization).

Everybody, come on.

Edited in April 2020-65438+April.

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Multiplication formula of 20 two-digit numbers multiplied by two-digit numbers

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