Total amount of work ÷ time = work efficiency (certain), and the total amount of work is directly proportional to time.
Total price ÷ quantity = unit price (certain), and the total price is directly proportional to the quantity.
Total dose ÷ time = unit dose (certain), and the total dose is proportional to time.
The width, area and length of a rectangle are the same.
The radius is proportional to the circumference.