[Hulka]

I teach college. I’ve discovered through class discussions that most students can’t make change, let alone understand that when you add a penny or two when you pay, this can sometimes reduce the amount extra change you get in return.

It is a concept most simply can’t understand.

[dfwgator]

I’ve discovered through class discussions that most students can’t make change,

Of course sometimes that can work to your advantage. ;)
Steve Martin - The Absent-Minded Waiter