Law analysis: the ten digits and the single digits in the obtained results are the product of the single digits respectively; The number on the most significant bit is equal to the product of ten digits multiplied by the number larger than it 1. The specific display is as follows:

AB× AB = {A× (A+ 1)} |× B}, that is,15 = {1× (1+1)} | {

Extended data:

Double-bit multiplication method

1, align the same numbers first, and then multiply from one number.

2. Multiply the multiplicand by the tenth digit of the multiplier.

3. Add two incomplete products.

Find a routine method:

1, serial number: to find a regular topic, usually a series of quantities are given in a certain order, and a general rule is found according to these known quantities. Find out the rule, usually the serial number of the package. So, put the variables and serial numbers together and compare them, and you will find the mystery.

2, first observe, what are the characteristics, and then check several commonly used methods in turn, such as differences, what is the operational relationship between adjacent three items, if the number changes dramatically, you can consider squares and cubes, but also be familiar with the values of some commonly used squares and cubes.

3. When encountering some series whose general term is difficult to be found by general methods, guess the general term formula of this series quickly and accurately through the first few items, and then prove it by mathematical induction or reduction to absurdity or other methods.