From the definition, we can know that divisor has two requirements, one is that the scores before and after divisor are equal, and the other is that the numerator and denominator are small. To meet two requirements at the same time, we should make use of the basic properties of fractions: the numerator and denominator of fractions are multiplied or divided by the same number at the same time (except 0), and the size of fractions remains unchanged.

So divisor is based on the basic properties of fractions, and numerator and denominator are divided by the same number at the same time. This divisor is the common factor of numerator and denominator. In general, if the calculation result can be simplified, it is generally given by the simplest score.

The key is to find the common factor of numerator and denominator, and then divide it by this common factor. It should be noted that some fractions may be easy to see the greatest common factor of numerator and denominator, and can be simplified to the simplest fraction at one time. When the number of numerator and denominator is large, we don't need to find the greatest common factor of numerator and denominator, but we can reduce it one by one until it is the simplest.

"The numerator and denominator of a fraction are divided by the same number (except 0) at the same time, and the size of the fraction remains the same-the basic nature of the fraction" for reduction. If the greatest common divisor of numerator and denominator can be seen quickly, it is easier to divide by their greatest common divisor directly.

The divisor is the formula divisor. Divide the denominator of a fraction by the common divisor at the same time, and the value of the fraction remains unchanged. The basis of reduction is the basic nature of fraction. If the greatest common divisor of numerator and denominator can be seen quickly, it is easier to directly remove it by their greatest common divisor.