divide the numerator and denominator of a fraction by a common factor at the same time, and the value of the fraction remains unchanged. this process is called reduction. the basis for reduction is: the basic properties of fractions.

for example, a/b is a fraction, a can be written as c*d, b can be written as c*e, then a/b can be written as d/e, because there is a common factor c that can eliminate the numerator and denominator at the same time.

simplest fraction: a fraction whose numerator and denominator have no common factors except 1 is called the simplest fraction.

note: when reducing a fraction, try to use verbal calculations. turning a fraction into a fraction that is equal to it but has a smaller numerator and denominator is called a reduction. when reducing a fraction, use the common factors of the numerator and denominator (other than 1) to divide the numerator and denominator of the fraction; usually divide until the simplest fraction is obtained.

when reducing divisions, if you can quickly see the greatest common factors of the numerator and denominator, it is easier to divide them directly by their greatest common factors.