Pigeon hole principle, level 6: "If more than kn objects are randomly divided into n rooms (k is a positive integer), then there must be (k+ 1) objects in a drawer".

The theory of "extraction principle" itself is not complicated, even obvious. For example, two puffs should have three apples, and at least one puff should have two apples, which is easy to understand.

With the increase of numerical value, it is difficult for students to reason and apply the "pigeon hole principle" to solve practical problems. Because of this, we don't need to be too strict in reasoning At the same time, it is helpful for students to solve practical problems by establishing mathematical models in class and accurately finding out who is a drawer and who is an object.

Basic expression of pigeon cage principle;

1. Put more than n apples into n drawers at will, so that there are at least two apples in at least one drawer (most commonly used).

2. Put more than m*n apples into n drawers at will, so the number of apples in at least one drawer is not less than m+ 1( 1 easy to understand).

3. Put an infinite number of apples into N drawers at will, so at least one drawer has an infinite number of apples (which will not be used in the exam).

Usually, if the high bending principle is used, the words "at least …" and "always …" will appear in the question.