1, figure 4 is to list four formulas according to the meaning of a picture. The fourth formula of a picture is mainly to let us observe the same picture from different angles, and list two addition formulas and two subtraction formulas according to the different meanings of the picture. It can help us to establish the connection of addition and subtraction and feel the integrity of knowledge.
2. There are three pieces of information on the diagram, and the relationship between these three pieces of information is often partial, partial and whole. When writing a formula, we have to adapt one of the information into a question and then write the corresponding formula.
3. Write the addition formula: the angle and order of observation are different, but the required questions are the same, all in order to find out what the whole is. Write different formulas and the result is the same. Write subtraction formula: different questions need different formulas. One is to remove the left part from the whole and find the right part. The other is to remove the right part from the whole and find the left part.
4. Four formulas in one figure means that four formulas can be listed through one figure, two of which are addition formulas and two are subtraction formulas. Primary school mathematics is to teach children a series of knowledge about number, four operations, the calculation formula of figure and length, unit conversion and so on through textbooks, which lays a good mathematical foundation for junior high school and daily life calculation. Frieden Noel, a Dutch educator, believes that mathematics comes from reality and must be rooted in reality and applied to reality.