In mathematics, the division of two numbers is also called the ratio of two numbers. In the ratio of two numbers, the number before the comparison sign is called the preceding item, the number after the comparison sign is called the latter item, and the quotient obtained by dividing the preceding item by the latter item is called the ratio. The basic property of the ratio is that the first and last items of the ratio are multiplied or divided by the same number at the same time (except 0), and the ratio remains unchanged.

Inverse ratio: if the preceding and subsequent terms of one ratio are the latter and preceding terms of another ratio, these two ratios are called inverse ratio, and the ratio of the two ratios is reciprocal; The ratio of 0 in the previous paragraph is not inversely proportional, because the latter term of the ratio cannot be 0;

Lian Bi: Three or more numbers can also be expressed by ratios. Such ratios are called Lian Bi.

Simplest integer ratio: the first and last terms of a ratio are ratios of prime numbers, which is called the simplest integer ratio.