1. Vertical back: for example, 1 1 gets one, 12 gets two, until 19 gets nine, then 22 gets four, 23 gets six, until 298, and then 33 gets nine, 342, until 3927. There is a rule in this method, that is, the number of digits in the vertical column increases gradually, which can help memory.
2, across the back: for example, the first row, sentence by sentence; The second sentence is two sentences, one sentence is two sentences, and two sentences are four sentences; By analogy, the first few lines are only a few sentences, and the last nine sentences range from 199 to 998 1. There is another rule in this method. In the first few lines, the last sentence is a few more than the previous one.
3. Looking back: For example, if you recite one or two first, you will get two, and then recite two or two to get four. At this time, turn it down and recite two or three to get six, and two or four to get eight until 298; Then go back to one three to get three, two three to get six, three three to get nine, and then turn down to three four twelve until three nine twenty-seven. One of the characteristics of this recitation is that there are nine sentences in the formula from one to nine, and several formulas will gradually increase.