2. The basic nature of the ratio:
The two items before and after the ratio of 1. are multiplied or divided by the same number at the same time, and the ratio remains unchanged except 0;
2. The front and back terms of the simplest ratio are prime numbers, and the front and back terms of the ratio are integers;
3. The ratio is usually expressed as an integer, and can also be expressed as a fraction or decimal;
4. The last item of the ratio cannot be 0;
5. The latter term of the ratio is multiplied by the former term of the ratio equal to the ratio;
6. The former term of the ratio is equal to the latter term.