First of all, the teacher said that the child didn't know arithmetic. This requires teachers to find a way to see where the children's understanding is difficult, rather than parents to find a way. Teachers must be more professional. Secondly, arithmetic in primary schools is mostly realized by students in operation, so that children can use sticks and cards more in calculation, and talk about the significance of calculation in combination with reality. Finally, it is also a personal opinion. Arithmetic is to help students master the calculation process. Understanding arithmetic is not temporary. There is a process that needs to give children time.