Additive associative law: a+b+c=a+(b+c)

Multiplicative commutative law: a*b=b*a

Law of multiplicative association: a*b*c=a*(b*c)

Multiplication and distribution law: a(b+c)=ab+ac.

The digits of the multiplier are added to the multiplicand to get the first product, and the digits of the multiplier are multiplied by the digits of the multiplicand to get the last product, which is full of ten and the first one.

For example: 15× 17

15 + 7 = 22

5 × 7 = 35

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255

That is 15× 17 = 255.

Multiply two numbers with the same bit but different bits.

Multiplier plus multiplier digits, sum multiplied by ten-digit integer, the product is the front product, and single digits multiplied by single digits is the back product.

For example: 43 × 46

(43 + 6)× 40 = 1960

3 × 6 = 18

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1978

A simple operation method with a coefficient of 1 1.

Minus one equals nine.

Ten plus complement method

The factor is1011001100.

Oral arithmetic multi-digit addition

1，a+b=b+a

2、a+b+c=a+(b+c)

3，a*b=b*a

4、a*b*c=a*(b*c)

5、a(b+c)=ab+ac

Additive commutative law: A+B = B+A.

Additive associative law: a+b+c=a+(b+c)

Multiplicative commutative law: a*b=b*a

Law of multiplicative association: a*b*c=a*(b*c)

Multiplication and distribution law: a(b+c)=ab+ac.