Adding and subtracting two digits means adding and subtracting one digit and integer ten on the basis of students' oral calculation of two digits. Because the teacher thinks that students have a good foundation of oral calculation before teaching this part, they only need to teach the method and format of oral calculation this time, and they have not grasped the key points and difficulties when preparing lessons, so the classroom teaching effect is not ideal. For this part of knowledge, students and teachers have many questions to reflect on. In fact, the students have recited the calculation rules of adding and subtracting two digits with a pen and can understand the calculation algorithm. It can be said that the column is vertical, but why is the answer wrong? After repeated thinking, I summed up their mistakes mainly as follows:

Within 1: 20, the calculation foundation of addition and subtraction is not solid and skilled. Many children are still counting with their fingers. I joked with them and said, "You don't have enough fingers. Do you want to use your toes? That's too much trouble! "

Two: when doing the problem, you are careless, don't pay attention to adding and subtracting symbols, and always copy the numbers or symbols wrong, for example, copy 23 into 32, and copy the plus sign into the minus sign.

Third: the numbers are not arranged properly. Some students arrange the numbers of one digit plus or minus two digits into ten digits, which leads to calculation errors.

Four: forget to write answers in horizontal style, forget to write units in application questions, etc.

Five: Some students calculate the answers orally and then write them in vertical body, or simply don't even have vertical body, but have horizontal body directly. Others worked out the horizontal answer orally, and then used the vertical calculation, resulting in two kinds of answers: horizontal and vertical.

In this regard, I constantly take some small measures in teaching to stimulate their interest in computing:

One: Let the students take the initiative to participate in the competitions such as driving the train and who is the fastest. Students are very interested.

Two: Let students be doctors, write some common mistakes on the blackboard, and let students correct them.

Correct homework face to face, so that students can correct their mistakes in time and not repeat them.

These measures have achieved certain results, but for those students with poor computing foundation, I don't think they can be improved overnight. They need to practice and do more and apply math problems to real life. At the same time, they should let students explore themselves actively with the help of existing knowledge and experience, so that every student has the opportunity of independent development and innovation, and our teaching efficiency will be improved.