The "Answer" (above) is easier to understand with some examples.
Example 1
If the #"value associated with some collection"# is how much some shirts cost e.g. #$60#
and the #"number of elements in the collection"# is #5# shirts,
then
#color(white)("XXX")"unit rate" = ($60)/5" shirts" = ($12)/"shirt"# or #$12# per shirt.
Example 2
Suppose I drove my car #300# miles and used #15# gallons of gas.
One way of determining a "unit rate" would be:
#"value associated with collection"#: #300# miles.
#"number of elements in collection"#: #15# gallons.
#color(white)("XXX")"unit rate" = (300" miles")/(15" gallons") =(20" miles")/"gallon"# or #20# miles per gallon.
Note that the "unit rate" could have been the reverse of this.
That is we might have been looking for a "unit rate" of gallons per mile.
I which case we would have
#color(white)("XXX")(15" gallons")/(300" miles")=(0.05 " gallons")/"mile"#
