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The coup of irregular perimeter in primary school mathematics
The secret of irregular figure perimeter in primary school mathematics is as follows:

We can transform these graphics into the sum-difference relationship of basic graphics by cutting and splicing, so the problem can be easily solved.

1, add.

This method is to decompose an irregular figure into several basic regular figures, calculate their areas respectively, and then add them to find the area of the whole figure.

2. subtraction.

This method regards the area of irregular figure as the difference of several basic regular figures.

3. Seek the law directly.

This method is based on the known conditions, and directly obtains the area of irregular graphics as a whole.

4. Reorganization method.

This method is to disassemble the irregular figure, reassemble it into a new figure according to the specific situation and the needs of calculation, and try to find out the area of this new figure.

5. Auxiliary line method.

This method is to add one or more auxiliary lines to the graph according to the specific situation, so that the irregular graph can be transformed into several basic regular graphs, and then add and subtract to solve it.

6. Cutting and repairing methods.

This method is to cut off a part of the original graph and make up another part to make it a basic regular graph, thus solving the problem.

7. Translation methods.

This method is to cut a part of the graph and move it to an appropriate position in parallel, so that it can be combined into a new basic regular graph, which is convenient for calculating the area.