Does unit rate always have to be on the bottom of a ratio?
No.
To determine the unit rate, you need to find the amount of one quantity in relation to one unit of another quantity. The unit rate can be written as a ratio, where the numerator represents the quantity being measured and the denominator represents the corresponding unit. However, it is not a requirement for the unit rate to always be on the bottom of the ratio.
In fact, the position of the unit rate in a ratio can depend on the context of the problem or the specific relationship between the quantities being compared. For example, if you have a ratio comparing the cost of 3 apples to $6, you can express the unit rate as either 3 apples for $6 or $6 for 3 apples. The important thing is to have a clear understanding of the relationship between the quantities being compared and to properly label both the numerator and denominator to represent the correct units.