"Wide Angle of Mathematics" is a newly added content in the second volume of the third grade mathematics textbook of compulsory education, which involves the overlapping of mathematics knowledge widely used in daily life. Set theory is the most basic mathematical thought, and set theory can be said to be the foundation of mathematics. Students have been using set thinking method since they began to learn mathematics.
Special case of mathematical wide angle:
1, chickens and rabbits in the same cage
Chickens and rabbits caged together is one of the famous anecdotes in ancient China, which was recorded in Sun Tzu's Art of War. The problem of chickens and rabbits in the same cage is a common problem in primary school Olympic mathematics. Many elementary school arithmetic application problems can be transformed into such problems, or solved by a typical solution-"hypothesis method". Therefore, it is necessary to learn its solution and thinking. Usually, the hypothesis method is simpler and easier to understand.
2. The principle of pigeon nest
There are ten apples on the table. If we put these ten apples in nine drawers, no matter how we put them, we will find at least two apples in at least one drawer. This phenomenon is what we call the "pigeon hole principle".
The pigeon hole principle roughly means: "If each drawer represents a collection, then each apple can represent an element. If there are n+ 1 elements in n sets, there must be at least two elements in a set. " Pigeonhole principle is sometimes called pigeonhole principle, which is an important principle in combinatorial mathematics.