If the title doesn't make sense I will try to explain via example.
There were 100 apples, 80 were purchased; 80% were purchased Add 100 to each, apples and purchases 200 apples, 180 purchased; 90% were purchased 300 apples, 280 purchased; 93.33% were purchased etc. Is there a formula/rule that can be applied which will show the relationship of the values?
I guess what I mean is, is there a rule governing by what increment the % purchased will change for each increment of 100 apples? What if it were 60 apples?