How to do the addition and subtraction of carry abdication within a hundred?

There are the following algorithms.

Methods :1Carry addition of two digits plus two digits:

Formula: add 9 to subtract 1, add 8 to subtract 2, add 7 to subtract 3, add 6 to subtract 4, add 5 to subtract 5, add 4 to subtract 6, add 3 to subtract 7, add 2 to subtract 8, add 1 to subtract 9 (note: the number of additions in the oral decision is to say the number in the single digit).

Example: 26+38=64 Solution: Add 8 to subtract 2, who subtracts 2?

6 on 26 minus 3 on 10 to 4. (Note: How to carry the ten digits on the last two-digit number, is 1 I enter 2, is 2 I enter 3, is 3 I enter 4, and so on.)

So where to carry it, to the first two-digit ten. For example, if this time it is 3 and I enter 4, it is 2+4=6 in the first two digits. Here, 26 + 38 = 64 is 6-2 = 4 written in the single place, and 3 into 4 plus 2 is equal to 6 written in the ten place.

Another example is 42 + 29 = 71. Just use the sentence to add 9 to subtract 1, 2-1 = 1, write 1 in the single place, is 2 I into 3, 4 + 3 = 7, write 7 in the ten place to get 71. This method has learned to be tried and tested, faster than a calculator.

Two digits plus two digits are not added in the number can be written directly, such as 25 + 34 = 59, the single digit plus the single digit is written in the single digit after the equal sign 5 + 4 = 9, and the ten digits plus ten digits are written in the ten digits can be 2 + 3 = 5, that is, 59. It is not necessary to calculate vertically.

Method 2Abdication subtraction of two digits minus two digits. Verbal Decision:

Formula: minus 9 to add 1, minus 8 to add 2, minus 7 to add 3, minus 6 to add 4, minus 5 to add 5, minus 4 to add 6, minus 3 to add 7, minus 2 to add 8, minus 1 to add 9. (Note:.)

The subtraction in the verbal duel is to say the number of subtraction in the single digit). Example: 73-46=27, solution:

To add 4 to subtract 6, who adds 4? 3 plus 4 equals 7 written in the single digit, the ten digit of the subtraction is 4, I retreat 5, who retreats 5? 7 back 5, that is, 27.

Note: How do I abdicate? The ten digits of the subtraction are 1 you retreat 2, it is 2 you retreat 3, it is 3 you retreat 4, and so on, but it must be a bit minus a bit and not enough to reduce the situation in order to retreat like this.

The above two methods were developed by using the method of making up the ten in the first-grade textbook. Their verbal decisions are more or less the same, just remember one of them, and the other method will be able to get together.

There are six algorithms:

Add one digit to one digit (add without carrying).

One digit plus one digit (carry plus).

Two digits plus two digits (carry plus).

Subtract two digits from two digits (non-abdication subtraction).

Two digits minus two digits (abdication minus).

Mixed addition and subtraction.

Carry addition within 100: the same digit alignment, unit and unit addition, ten and ten digits added, full ten to the previous digit within the abdication subtraction: the same digit alignment, unit minus a digit, ten digits minus ten, the single digit is not enough to subtract from the ten digits 1.

There are many pen additions and subtractions within 100.

For example: 12.67 plus 3.39, 22.14 plus 45.6, 77.39 plus 21.34, 61.79 plus 25.67, etc. Eighty-five points and one hundred and one minus seventeen points and ninety-seven, fifty-two points and two hundred and twenty-six points and so on.

Calculation rules for two-digit plus two-digit addition:1. Align the same digits.

2. Add from single digits.

3. The single digit is full of ten to ten to 1.

The two-digit minus two-digit pen algorithm is:1. Align the same digits.

2. Subtract from the single digit.

3. If the single digit is not enough to subtract, retreat 1 from the 10th digit, add 10 to the single digit and then subtract it.

The following is the calculation of abdication subtraction within 100.

Method: 1. Dismantle 10 methods. Quite simply, split the minus number into a 10 and another number, for example:

43-7=？We can ask the child to split 43 into 10 and finger 33, first using 10-7=3, then 3+33=36. Parents can draw a picture for their child, so that the child may be able to solve the problem more intuitively.

2. Borrow 10 methods. As the name suggests, because the number on you is less than the subtraction, we borrow 10 from the tenth, for example: 43-7=?

We borrow 10 from 10 digits and it becomes 13, that is, 43 is divided into 30 and 13, and we use 13-7 = 6, plus 30, and the answer is 36.

3. Make up 10 methods. The method of splitting 10 and borrowing 10 are to split the subtracted number, and the method of making up 10 is to make up the subtraction less than 10 into 10, this method is suitable for the number where the subtraction is 6-9, because 6-9 is close to 10, we can subtract 10 first, and add the excess subtracted number.

4. Column vertical type. This or take a method is suitable for the number of minus is also more than 10, the vertical listing can clearly allow children to use everyone to subtract everyone, ten digits minus ten, but also pay attention to the number on the single digit if it is less than the single digit of the minus.

Very fast. 8 minutes is already a very fast speed, let alone 3 minutes, which is a bit too short.

In fact, in real learning, speed and time are not important, what matters is the child's mastery of knowledge. In addition to this, the cultivation of mathematical thinking is also very important.

Clever games to stimulate children's "living" thinking in life

Let students learn by playing, playing tricks, playing with interest, and playing with knowledge, which is an effective means of cooperation to develop thinking. Students experience life through games, reap the fruits of cooperation, and feel the joy of success.

Skillfully set up operations to cultivate children's ability to "live" in life

Avoid using all arithmetic definitions and laws and guide children to do as much hands-on work as possible. The operation is to make students perceive intuitively, learn independently, cooperate and form their abilities through swinging, dividing, moving, and talking. This is an effective way to bring math problems to life and a great way for students to discover definitions on their own.

1. First of all, teach children numbers within 30 and addition within 20.

addition and subtraction within. It is the division and combination of numbers. This is the basis of all addition and subtraction and must be mastered.

The abdication subtraction within is to abdicate the whole number of tens first, and then subtract the number.

It is still based on addition within 20 and subtraction within 10.

4. When you teach your child, you tell him to do it directly.

It's best to do the column calculations vertically, so that it is simple and straightforward. Do more practice questions so that you can master them quickly.

5. The key lies in the foundation. The child's learning ability is very strong, don't worry about whether he will know it or not, you just teach him repeatedly, he will learn, you have to believe in your child. The key is revision. Encourage your child.

1. Be able to count down from "1" proficiently.

2. Be able to skillfully start counting from a certain number in the middle.

3. Be able to skillfully count down from a certain number in the middle.

12-9=x small sticks are bundled into a bundle of 10 sticks, and two are placed separately. Remove 9 from 10, leave 1, and then combine with 2 to make 3. Initially understand the truth that it is not enough to reduce and retreat one to ten.

Learn addition with carrying, and subtraction with abdication up to 20.

It is a difficult point for children from preschool to first grade. Children are very easy to accept addition and subtraction within 10, the fingers are exactly ten, and breaking the fingers is very direct and simple.

Abdication subtraction within 20

Do not carry within 20, including change without abdication addition and subtraction is:

One, ten plus a few equals a dozen.

2. A dozen minus a few equals ten.

3. The number on the single digit is just right to subtract the number on the single digit, and the number on the single digit is (0).

Fourth, a dozen plus a few blind old calls do not carry addition: ten digits remain the same, and the single digits are added. (10 plus 10, single digit plus 1).

12 + 3 = 15 13 + 4 = 17 15 + 12 = 27 11 + 19 = 30 (although it exceeds 20, but there is no carry, the grinding method is OK.) ）

Fifth, the non-abdication subtraction of more than a dozen minus: the ten digits remain unchanged, and the single digit is subtracted. (10 minus 10, single digit minus 1).