What does it mean that the lower beads in the beads are not enough to add a pair of lower nines

Double under is the upper bead and the lower bead at the same time to dial down, such as 4 + 1, the lower bead is not enough to add, double under 9, that is, the upper bead 5 and the lower bead 4 at the same time to dial down, the result is 5That's what it means. Subtraction is the opposite.

This is the calculation essentials of addition and subtraction in mental arithmetic:

The essentials of its addition are: add to see the outer beads, enough to add straight addition, not enough to add double under the supplement, full ten into one subtract the number of complements.

The essentials of subtraction are: subtract the inner bead, enough to subtract the straight addition, not enough to subtract the double upper supplement, and add the number of full ten to one plus the supplement.

The specific fingering needs to systematically learn the latest and most scientific mental arithmetic addition and subtraction essentials in China; According to the new arithmetic algorithm, it depends on the specific question type! Specifically, you can learn to communicate.

Shanghai Mental Arithmetic Shanghai Orthodox Mental Arithmetic Two-handed Bead Sharing: 9+9 The index finger and thumb of the right hand dial 9 on the abacus unit

9 (using the mantra +9=-1+10): minus 1 from the index finger of the right hand, add 10 to the thumb of the left hand at the same time, answer 18

For example: 6+9

The boring mantra becomes an easy-to-understand nursery rhyme, which is easy for children to accept and memorize.

To learn to add or subtract beads, we must first memorize the formula, and the original formula in the abacus mental arithmetic textbook is relatively simple.

1. Boring, many children can't remember, some children remember it temporarily, but it doesn't take long to forget. In response to this situation, I often organize children to make up formulas into nursery rhymes in teaching, and perform while reading, such as when learning the addition and subtraction of complements, I and children together make up the complement formulas into nursery rhymes:

Add one, please dial double under nine, we are all good friends;

Add two, please dial double under eight, laugh when you are happy;

Add three to dial double and seven, sometimes you will be angry;

Add four, please dial double under six, and jump and jump when you are happy.

Subtract one, dial double on nine, and sing to learn larks;

Minus two, please dial double on eight, don't procrastinate too much;

Minus three, please dial double on seven, and queue up to do exercises neatly;

Minus four, please dial double on six, and don't sleep lazy in the morning.

Because teachers actively mobilize children to make nursery rhymes with teachers, children like to learn and are willing to perform, so they remember the mantra very firmly, so as to further improve children's understanding and memory ability.

Addition and subtraction of complements: When adding, this file should be full of ten, and add a complement;

When subtracting, this file is not enough to reduce, and the number of retractions is also reduced.

Pick bead fingering: enter a double point, retreat a double together.

Bead mantra. 1, plus one: into a double point nine minus one: back a double into nine.

Plus two: Advance one double into eight minus two: Retreat one double into eight.

Plus three: advance one double into seven minus three: return one double into seven.

Add four: advance one double into six minus four: return one double into six.

Add five: advance one to five minus five: retreat five.

2, add six: four (4 + 6) minus six: one back four (10-6).

Add seven: go three (3 4 + 7) minus seven: go back one and go up three (10 11-7).

Add eight: go two (2 3 4 + 8) minus eight: go back one and go up two (10 11 12-8).

Advance and retreat direct addition and direct subtraction: there is no complement when overdue, and there is no complement to return when subtracting.

Bead fingering: Pluck up with both hands and pluck down with both hands.

1, plus one: into a double point nine minus one: back a double into nine.

Plus two: Advance one double into eight minus two: Retreat one double into eight.

Plus three: advance one double into seven minus three: return one double into seven.

Add four: advance one double into six minus four: return one double into six.

Add five: advance one to five minus five: retreat five.

2, add six: go into four (4 + 6) minus six: back one on four (10-6) plus seven:

Advance three (3 4 + 7) minus seven: retreat one on three (10 11-7) plus eight: advance two (2 3 4 + 8) minus eight:

Retreat one on two (10, 11, 12-8).

Advance and retreat direct addition and direct subtraction: there is no complement when overdue, and there is no complement to return when subtracting.

Jiuzhu only has a formula when carrying or abdicating, such as going to make up for one, borrowing one to make up. The nine-bead algorithm cannot be regarded as mental arithmetic, but only a tool for calculating enlightenment learning, similar to the Russian ten-bead abacus. Strictly speaking, abacus is the use of the five-bead abacus, and it is also the abacus commonly used in international mental arithmetic learning.

Because according to the famous "black bean experiment", the limit of human fast visual discrimination ability is 5 beads, and the accuracy rate is reduced if it exceeds five, which can also show that the error rate is quite high in rapid calculation, and the number of digits cannot be expanded once it is expanded. This is also the reason why there are almost no players who come out of the Jiuzhu algorithm in various competitions across the country.

There is no way to talk about intellectual development, which is just a simple calculation. Therefore, the nine-bead algorithm cannot be equated with mental arithmetic, and it is not the so-called "upgraded version of mental arithmetic", but it is just a clever use of the name of mental arithmetic to attract people's attention!

Is it children's mental arithmetic?

If so, such a mantra is completely unscientific!

Including what upstairs looks inside and out

There is no way for children to understand and digest such language!

I have seen the mantra of the landlord You should be talking about +1 double complement 9, +2 double complement 8, +3 double complement 7

Including subtraction, it's like this

I don't know if you're learning mental arithmetic If a question is 5+8-7+6-7, then how to say this formula

Believing that it can be said is completely inconsistent with the child's ability to understand

To solve this problem, you first have to understand what complements are! 1-9, 2-8, 3-7, 4-6, 5-5 are complements! In addition and subtraction within 10! If you encounter that the lower bead is not enough, you can use the double complement! For example:

4 + 1 first dial in 4, then add 1, the following is not enough to add, this time is to add 1 double under 9 (because the complement of 1 is 9), the index finger controls the upper bead (that is, 5) the thumb controls 4 lower beads (9 is composed of 5 and 4), dial it down together, equal to 5.

4 + 2 first dial in 4, then add 2, the following is not enough to add, this time is to add 2 double under 8 (because the complement of 2 is 8), the index finger controls the upper bead thumb controls 3 lower beads (8 is composed of 5 and 3), dial it down together, equal to 6.

And so on

But to be honest, I don't support this kind of learning method!