So for the past few months I’ve been telling my kids that, every time they write , they kill a puppy. In fact, I will hereafter refer to that equation as the **Dead Puppy Theorem**, or DPT. Since its discovery in early September, my students’ usage of the DPT has accounted for more canine deaths than heartworms.

# Tag Archives: modular arithmetic

# Paraskevidekatriaphilia

It’s going to be a bit of a strange year for Friday the 13ths. First of all, there will be three of them. Now that’s not *especially *weird–it happens every few years–but it’s the first time since 1984 that they’ll be spaced precisely 13 weeks apart. It’s also the last time until 2040 that we’ll have three of them in a leap year. I got all this information from a story on the *USA Today* website, which featured some words from one Dr. Tom Fernsler of the University of Delaware, a math professor (naturally) who’s earned himself the nickname of “Dr. 13.” An interesting tidbit from the good doctor, and bad news for the phobic: the 13th of the month is actually more likely to occur on a Friday than any other day of the week–688 times in a 400-year period.