The method of filling ten is the basic idea of carry addition within 20. By using the method of filling ten, the carry addition within 20 can be transformed into the familiar problem of 10 plus several, which makes it difficult and easy. For example, 9+5, divide 5 into 1 and 4, because 9 adds up to 10 and lacks 1, so it is divided into 1.

Teaching objectives:

1, let students calculate the carry addition of two digits plus two digits within 50.

2. Enable students to use what they have learned to solve problems in life.

3. Cultivate students' cooperative consciousness and the ability to summarize calculation methods through practical operation.

(1) The same number is aligned; ?

② Count from the unit; ?

(3) When the number of bits reaches 10, it can be marked with "1".

way

When two numbers are added, every time the result of a certain bit is greater than or equal to 10, you need to count 1 to the next bit, which is the carry. For example:

48

+ 56

————

= 104

8+6 = 14 & gt； 10 rises by one place (ten places) to 1.

4+5 plus rounded 1, that is, 4+5+ 1= 10 also needs to be rounded up by one bit (ten bits) to 1.

When there is carry addition in the operation, it is called "carry addition".

Baidu encyclopedia-carry addition