How to judge positive proportion and negative proportion

How to judge positive proportion and negative proportion


Generally speaking, the product of multiplication of two quantities is a fixed value, and the two quantities are in positive proportion
The quotient of the division of two quantities is a fixed value. In this case, the two quantities are inversely proportional



Judge whether the two quantities in the following questions are in positive proportion, and explain the reasons
If the deposit interest rate is fixed, is the principal and interest proportional? Why?
Please use the form "because... So..."


The time of deposit also determines the interest