The method and principle of the enumeration method of Olympic numbers in primary schools is to list all possible situations when studying problems, which is called enumeration method.

When using enumeration method to solve problems, it is often necessary to classify the objects discussed properly, otherwise it will be impossible to enumerate, or the problem-solving process will become tedious, especially if there are many or even infinite objects to be discussed.

There can be no omissions in the enumeration. Of course, there must be no omissions in the classification, that is, every research object should be in a certain category. It is generally best not to repeat the classification, but sometimes repetition will not cause mistakes or complicate the solution, so there is no need to be demanding.

The method of narrowing the enumeration range is called screening method, which follows the principles of determining the range, testing one by one, eliminating no solution and solving.

Example: It is known that the product of three numbers A, B and C is 10. What are the possible numbers a, b and c?

Analysis: When looking for the answer to the question, we should strictly follow the enumeration principle. Because the factor of 10 is 1, 2,5, 10, a, b and c can only use these four natural numbers, and the shilling number is 1, 2,5,65438+.