Quickly calculate the formula with your fingers

Know the numbers represented by hands and fingers

The first step in learning the fast finger algorithm is to know your own hands. In order to attract children's attention, let children play finger games first, palms inward, five fingers straight, let children observe their thumbs up alone. Next, remind the child that the left hand represents ten digits, the right hand represents one digit, the thumb represents five digits, and the other four fingers represent 1. On the basis of thumb, the index finger, middle finger, ring finger and little finger represent six, seven, eight and nine respectively, so that the five fingers can represent the number nine. When the right hand is more than nine, it will be closed with five fingers to indicate 0, and the left index finger represents 10, which is a decimal. This repetitive cycle represents every number from 0 to 99, supplemented by the movements of your feet, which can represent a hundred numbers within 300. When teaching young children, we must repeatedly emphasize that "the left hand is ten and the right hand is one". And use the finger positioning formula to help children distinguish.

(1), finger formula (hand exercise)

The index finger extends "1" and the middle finger extends "2";

The ring finger is "3" and the little finger is "4";

Hold your thumb with four fingers and remember that the thumb is "5".

(2), finger positioning formula

I have a pair of hands, representing ninety-nine; Set the left hand to ten, and I can count to ninety;

Pose your right hand and count from one to nine; It's convenient to add and subtract, so don't worry about calculation.

(3), two fingers exercise training formula (first ten, then one)

Ordinal number: eleven, twenty-two, thirty-three, forty-four, fifty-five, sixty-six, seventy-seven, eighty-eight and ninety-nine.

Countdown: ninety-nine, eighty-eight, seventy-seven, sixty-six, fifty-five, forty-four, thirty-three, two is two, eleven.

Digital finger translation training

After children understand the numbers represented by their hands, they are required to report the numbers as soon as they see the gestures, that is, translate the numbers; On the contrary, when you hear numbers, you can point out your fingers, which is digital translation. Digital-to-digital translation training should first let children learn to read gestures, and teachers should start pointing out numbers to children. Among them, we should pay special attention to the differences between 1 and 5, 2 and 6, 3 and 7, 4 and 8 (the thumb can not be ignored), and let the children compare them repeatedly until they are proficient. Then the teacher said that numbers are represented by children's fingers. When representing two digits, in order to avoid the confusion that children express 56 as 65, that is, both hands are ten digits, children should be reminded to express ten digits first and then one digit. For example, if you represent 35, you should give 3 for your left hand first, and then 5 for your right hand. In the initial training, children can give while reading, which is easy to master.

Direct training within ten minutes of study.

Children can learn direct addition within 10 after mastering the translation of numbers and fingers. The formula for direct addition within 10 is as follows:

1+ 1 1+2 1+3 1+5 1+6 1+7 1+8 2+ 1 2+2 2+5 2+6 2+7 3+ 1

3+5 3+6 4+5 5+ 1 5+2 5+3 5+4 6+ 1 6+2 6+3 7+ 1 7+2 8+ 1

In this part of the training, pay attention to remind children to standardize the operation when expressing each number with their fingers, especially the number 8 to practice specially; Secondly, when representing numbers, pay attention to the height of your fingers with your nose, and don't shake your fingers back and forth, which is convenient for children to operate and look at numbers.

Learn direct reduction training in ten minutes.

After learning the direct addition exercise, I began to train the direct reduction within 10, and the formula of direct reduction within 10 is as follows:

1- 1 2- 1 2-2 3- 1 3-2 3-3 4- 1 4-2 4-3 4-4

6- 1 6-5 6-6 7- 1 7-2 7-5 7-7 8- 1 8-2 8-3 8-5 8-8 9- 1 9-2 9-3 9-4

9-5 9-6 9-7 9-8 9-9

Learn five plus training in ten minutes.

In fact, quick calculation with fingers is an evolution of ancient abacus. The thumb represents the upper bead 5, and the other four fingers represent the lower bead, one for each. Some formulas can be added or subtracted directly, but some formulas need to be rounded by 5: for example, 1+4, the first one is 1, and then the fourth one is not enough, so we can only ask for 5 help, but the condition for asking for 5 is to accept 1. So when practicing adding five, let the children find out the friends whose two numbers add up to five (1 has a friend of 4; 4' s friend is1; 3' s friends are 2; The friend of 2 is 3), which is convenient for children to remember the following calculation formula after finding the right friend.

The formula of five addition is:

4 charge 1 out of 5 3 charge 2 out of 5 2 charge 3 out of 5 1 charge 4 out of 5.

The formula for adding five is as follows

1+4 2+4 3+4 4+4 2+3 3+3 4+3 3+2 4+2 4+ 1

For example; 3+4 (first 3+4, 4 is not enough, you can directly use the formula of 4 to get 1 and 5, which equals 7). This link is difficult for children to understand at first, but it is especially easy to master after mastering it.

Learn to break five and reduce training in ten minutes.

After mastering the calculation of five plus within 10, I began to learn the method of breaking five minus within 10. First of all, we should be familiar with the formula of breaking five and subtracting five:

1 out 4 in 5 out 2 out 3 in 5 out 3 out 2 in 5 out 4 out 1 in 5.

Within 10, the formula of breaking five and subtracting is as follows:

5- 1 5-2 5-3 5-4 6-2 6-3 6-4 7-3 7-4 8-4

For example: 7-3, give 7 first, give 2 directly with the formula of 3, and get 5, which is equal to 4. Children must be distinguished in this link, and the formula of adding five must be collected first; Moreover, the formula of breaking five and subtracting five should be given first and then collected.

Learn to increase or decrease training continuously within ten minutes.

This is a comprehensive exercise of direct addition and subtraction and five-plus-one-break, which helps children master the addition and subtraction operation within 10. For example: 3+5-6 5-3+4 7-2+3 9-6+5 and other formulas for children to practice.

Learn to carry and train

Formulas for carry and addition:

9 in 65438+0 in 65438+0 in 65438, 0 8 in 65438+2 in 65438, 0 7 in 65438+4 in 65438+0 4 in 65438.

3 into 7 1 2 into 8 1 1 into 9 1.

The formula of 10 is1+92+83+74+65+56+47+38+29+1.

For example: 2+8 (the first digit is 2, then the formula of 8 is 2, and the decimal digit 1)= 10.

Learn to abdicate and reduce training.

Abdication reduction formula within 10

1 return 1 return 9 2 return 1 return 8 3 return 1 return 7 4 return 1 return 65 6 return 1 return 4.

7 returns 6543 8+0 returns 3 8 returns 1 returns 2 9 returns 1 returns 1.

The formula of abdication reduction within 10 is as follows:

10- 1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9

For example: 10-7 (take out the tenth 1 first, and then use the abdication formula of 7 to return 1 to the third place) = 3.

The above exercises are the practice methods of addition and subtraction within 10 for large class children. Children like this method very much. It is helpful for children's intellectual development to perform operations and calculations while playing finger games. But also has high calculation accuracy, and is especially suitable for kindergarten children to learn. If you want to calculate the exercises within 20 or even 100, you can continue to explore and summarize on this basis.

Note: right index finger 1, 6. Right thumb 5. Left index finger10,60. Left thumb 50.

5+6 5+7 5+8 5+9 6+6 6+7 6+8 7+6 8+6