Multiplication of two digits is a basic mathematical calculation method that is widely studied after the fourth grade of primary school, and it is also an essential content for learning mathematics in the future. For mathematical operation, learning the skills of two-digit multiplication and fast calculation is of great help to improve the efficiency of mathematical operation and improve the examination results. The fast algorithms of multiplying two digits by two digits include head-to-head method, tail-to-tail method and tail-to-tail method; After a head is added with 1, the head is multiplied by the head and the tail is multiplied by the tail; The heads are complementary and the tails are the same; After adding 1 to the head, the head is multiplied by the head, and the tail is multiplied by the tail.

1, head-to-head, tail-to-tail, tail-to-tail: this algorithm can be used directly when there are more than dozens, but it must be noted that if the number of digits is multiplied, 0 should be used to occupy the position when there are not enough two digits.

2. After adding 1 to a header, the header is multiplied by the header, and the tail is multiplied by the tail: this sentence means that the headers are the same, and the tails are complementary, mainly that the first and the second are all ten, that is, the ten digits are exactly the same, and it can be used directly when the sum of the single digits is just equal to 10. In a two-digit multiplication formula, if the ten digits of two multipliers are the same, first add the single digits of the first multiplier to the second multiplier, and then add the mantissa. ?

3. Head, head and tail: This sentence means that the heads are complementary, the tails are the same, and the last one is the same as the first ten, and the single digits are exactly the same. When the ten digits just add up to 10, it can be used directly. If the single digits of the two multipliers are the same, the ten digits are multiplied and multiplied once, and the mantissa digits are multiplied again. It should be noted that the product of two numbers with the same digits is the last two digits of the number. If it is less than 10, just add 0 to the ten digits. .

4. After adding 1 to a header, the header is multiplied by the header and the tail is multiplied by the tail: the first multiplier is complementary, and another multiplier is used when the numbers are the same. Also pay attention to a knowledge point, that is, one-digit multiplication. When there are not enough two digits, use 0 to occupy a place.

Mathematical speed algorithm refers to the calculation method of fast addition, subtraction, multiplication and division by using the special relationship between numbers. Mathematical quick calculation methods are divided into Jinhua quick calculation, Wei quick calculation, historical quick calculation and "swallowing gold in the sleeve" created by the ancients.