The multiplication formula of 9 also has a special rule of using hands, so we can also use the "finger memory method" to help us remember the multiplication formula of 9, and use 10 fingers to remember it, so that students are interested and remember it well!
Please hold out your hand. When memorizing the formula "nine out of ninety", we can bend the little finger of our left hand. On the right of the bent finger, there are nine fingers. The "9" here stands for 9 in every place. Similarly, when writing "298", bend the ring finger of the left hand and the left side of the finger.
There is a heel finger, where "1" represents the number 1 at the tenth position in the product, and there are eight fingers on the right side of the bent finger, where "8" represents the number 8 at each position in the product, that is, "298".
Counting from left to right, the first finger bends to represent the number nine, the left side of the bent finger represents the tenth digit of the product, and the right side represents the number of the unit of the product.
Other methods of memorizing the multiplication formula of nine skillfully;
1, compare the laws: such as 594 15, 6954, 796 13 and 4936.
2. Tell the story: Tang Priest experienced eighty-one difficulties, the Monkey King changed in 8972, Pig Bajie had only half the mana, and changed in 4936.
3. Use homophony to remember: Uncle 8 1 year (998 1).
4. Observe the unit and the origin of the tenth place: multiply by nine, the tenth place is a few minus 1, and the unit is the number on the tenth place minus nine, such as 4936.
The origin of occupation:
The formula for primary school students to learn "primary ninety-nine" is from "11" to "998 1", but in ancient times it was the other way around, from "998 1" to "224". Because the first two words of the formula are "99", people call it "Xiao 99" for short.
Only in the 13 and 14 centuries did this turn around, "one by one gets one, 998 1".