We had just had a client ask why the layout on a 4"x9" card significantly different from what was on a 20"x30" poster for the same event. 

Me: These are not proportionally equal. Things have to be moved around. Even with full page to a half page there has to be some tweaking, even if the elements are a high-enough resolution for both. One is long and skinny, the other is a bit fatter and shorter. 

Client: (in a huff) Well, we all can’t have the fancy degrees you have.

*Editor’s Note: Proportions and ratios are usually taught by the eighth grade in North America.