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How to teach addition and subtraction of mathematics in large classes within 20
1, let children learn to count skillfully. Requirements are:

(1) can count down from "1" skillfully.

(2) be able to count skillfully from a certain number in the middle. For example, the teacher said: count from 4; Count from 12.

(3) be able to count down from a certain number in the middle skillfully. Example: The teacher said: Count down from 4, and count down from 12.

2. Let children master the relationship between numbers: for example, what is in front of 5? What's behind? 8 What's ahead? What's behind? Count forward from 5, count backward, count forward from 1 1, count backward.

Step 3: Let children master the relationship between numbers: for example, which is bigger, 7 or 8? 12 or 4, which is bigger?

4. The fourth step is to let the children learn to read the questions. Many children can read the questions, but they can't understand them. Children know the ways of "+"and "-",but they don't know how to read them. Let the children read it out and do the next calculation. Tell them to count backwards when they read "add". When you read "minus", you count forward.

5, the fifth step, teach children to know the unit and ten, so that children can skillfully say what is the unit in the two-digit number and what is the ten?

For example: 15, the unit is 5, and the decimal number is 1.

6. Addition and subtraction of hand index:

(1) Example of addition: 15+2= We tell our children to keep the big number 15 in mind, and use their fingers to indicate the small number 2 (let the children put out their fingers) with a "+"sign in the middle, that is, from 15,65438+.

(2) Subtraction, such as: 15-2= We tell our children that the big number 15 is safe, the small number 2 is expressed with a finger (let the child put his finger out), and the middle is marked with a "-",that is, counting backwards from the previous number 15, and the previous number 65438 is.

(3) addition and subtraction of numbers:

Addition, for example: 15+2= We tell children that the sum of one digit and one digit is 5+2=7, and the sum of ten digits and ten digits is 1, so 15+2= 17.

Subtraction, such as: 15-2=, we tell children that the subtraction between one bit and one bit is 5-2=3, and the subtraction between ten bits is 1-0= 1, so 15-2= 13.

7. Relatively speaking, "counting fingers" only applies to the addition formula in which one of the two numbers is singular, because if both numbers are even, then the fingers are not enough; Although difficult to learn, "addition and subtraction of numbers" can be applied to all formulas. From the perspective of sustainable development, it is suggested to use "addition and subtraction of numbers".