parties tend to have the 15% "gratutity" added on, as large parties are generally known
to not be able to figure out what 15% of their bill (before tax, before coupons) is. But in America it seems that nobody can. Plastic cards about the size of credit cards have popped up which show
the proper tip to give given the amount of money your bill was for (generally it goes in increments of 50 cents or one dollar). When we can't figure out what 15% of $15.00 is (for all you curious out there, it's
$2.25 - and I didn't use a calculator for that), something is wrong with the world. Or maybe it's the opposite (loud scoff, just for effect), and my favorite quote applies - "The more advanced mathematics you know, the lower your ability to add correctly." Or tip, in this case. So if you're a waitperson, be nice to the bearded math professor who just gave you a completely random amount of money.