It's time once again to mix a math with a little magic!

Let's start with a favorite of mine, the Day of the Week For Any Date feat. In order to keep it simple enough to do in your head, the version on my site uses only 3 variables.

In the current issue of Plus Magazine, they feature an article on this same feat, but it makes it easier by using more variables. This sounds contradictory, but if you've ever had trouble memorizing the 100 keys for the years 00-99, you might appreciate this approach.

Instead of memorizing 100 numbers, you're remembering only 42 items (12 month codes + 12 decade codes + 18 leap year offsets). The leap year offsets have a pattern of their own, which makes them even easier to remember! As a bonus, the article includes video of Grey Matters' favorite Arthur Benjamin performing the calendar feat, so you can get an idea of what it should look like when you do it.

A little less than 2 years ago, I discussed the Fitch Cheney card trick. This trick's deceptively simple appearance and efficient method have made it a classic. There's some great mathematical lessons you can learn from this effect, as discussed in this Math Horizons article (PDF) and in this Numericana article (don't miss the related generalization article, too!).

Since you need a secret assistant, however, this isn't always easy to practice. Magician Larry Finley, however, has come up with an excellent solution. Over at the Magic Cafe, Mr. Finley shows you how to prepare a spreadsheet that helps you practice the Fitch Cheney card trick! You need to read through this article and follow the directions carefully, but it really is a great way to practice this trick!

Finally, we'll round out these tricks with one that's completely new to me. The best thing about the following math-based effect is the complete lack of any mathematical appearance to the effect! It's from our old buddy Scam School, and it's alternately known as Assassination, or the simpler Predict A Friend's Poison Cracker!.

Before the effect itself begins, there are a few good bar bet-style stumpers that you may want to remember. Here's an additional challenge: As you watch the video, stop it at the 8 minute mark (8:00), and see if you can work out for yourself the method. I've already given you the clue that it's mathematical, so try and see if you can work out the math.