Perimeter can only be used on two-dimensional figures (planes and surfaces), and three-dimensional figures (solids) such as cylinders, cones and spheres can't express their boundary size by perimeter, but by total surface area.
Methods of learning mathematics
1, the most important thing in learning mathematics is the ability to solve problems.
If you want to do math problems, you must have a lot of practical accumulation and know the steps and methods to solve various problems. If you do more questions, you will feel it. If you come up with similar questions, you will have a solution idea.
2. Second, learn to preview.
The idea of solving problems is not directly available, nor can it be easily obtained by simply doing a few questions, but accumulated in the preview process. Therefore, preview plays a very important role in the process of mathematics learning. On the one hand, preview can make everyone know something about mathematics in advance, on the other hand, it can cultivate students' autonomous learning ability in mathematics.
3. When learning mathematics, you must do more problems.
After understanding the basic definition and knowledge points of mathematics, we need to consolidate our knowledge by doing corresponding exercises. Only by doing more and practicing more can we master what we have learned better. It is easier to look at flowers than embroider when learning mathematics. Only when you really do the problem and experience the actual operation can you learn.