1, the same tail is complementary, the first digit is multiplied by a larger number, and the product of mantissa follows. Such as: 23×27=62 1.
2. The tail is complementary to the first, the product of the first plus the tail, and the product of the mantissa follows. Praise and Debate: 87×27=2349.
3. If the first digit is a mantissa complement, reduce the square of the first and last digits of a large number. Such as: 76×64=4864.
4, the last bit is one, the product of the first bit is followed by the sum of the first bit, followed by the product of the mantissa. Such as: 51× 21=1071.
Law of multiplication:
1, the multiplication of integers meets the following requirements: commutative law, associative law, distributive law and elimination method.
2. With the development of mathematics, the object of operation has developed from integer to more general group.
3. Intra-group multiplication is no longer needed to satisfy the commutative law. The most famous noncommutative example is the quaternion group discovered by Hamilton. But the law of association is still satisfied.
Law of multiplication and exchange: early loose ab=ba, note: letters are multiplied by letters, and the multiplication sign can be written without writing.
The law of multiplicative association: ab(c)=a(bc). Yeda
Multiplication and distribution law: (a+b)c=ac+bc.