On the proportional formula in primary school mathematics;

1, distance: time = speed (certain), distance is proportional to time.

2. Workload: working hours = working efficiency (certain), and workload is directly proportional to working hours.

3. Total price: quantity = unit price (certain), and total price is directly proportional to quantity.

4. Distance on the map: actual distance = scale (certain), and the distance on the map is directly proportional to the actual distance.

Characteristics of direct proportion:

1, when the value of x and the value of the independent variable in the inverse proportion are also converted into its reciprocal, the inverse proportion is converted into the positive proportion. When the value of x in a positive proportion (the value of independent variable) is transformed into its reciprocal, it is transformed from a positive proportion to an inverse proportion.

2. The proportional image is on the light passing through the origin. It develops from the intersection of the abscissa and ordinate of the statistical table, along the diagonal line from the lower left corner to the upper right corner, and extends out of the table. In the sense of direct ratio, it can extend downward, so it is considered as a straight line.