Tax Day

Income tax is due today. Here’s a good, clean joke for April 15:

A nickel rolled down the hill. Why didn’t the quarter follow her?
Because it had too much cents!

April 15 is National High Five Day

The third Thursday of April is National High Five Day. In 2010, that’s today! Normally, I ignore made up holidays like this, but there are (at least) two great math problems that involve high fives. So if acknowledging a silly fabrication means I get to share some math, then I’m all for it.

Here are the problems I know related to high fives:

There are five players on a basketball team. When the star player hit the winning free throw at the end of regulation, she and each of her teammates gave each other a high five. How many high fives occurred?

You could also ask this question in the opposite direction (though it’s really the same question):

My friends and I were watching a Penn State football game. When Penn State kicked the winning field, my friends and I gave each other high fives. Each friend gave exactly one high five to every other friend. A total of 36 high fives occurred. How many friends were watching the game with me?

But, in my opinion, here is the best variation of this problem:

My wife and I play on a softball team with four other couples. After I hit the game-winning home run at a recent game, a lot of high fives occurred among the players on our team. But not everyone got a high five from everyone else, no one got a high five from his or her spouse, and — obviously — no one high fived himself. Later, I asked each of my teammates how many high fives they received, and everyone gave me a different response. How many high fives did my wife get?

Now, don’t you agree that those questions make celebrating National High Five Day a reasonable thing to do?