360 was created as a place to share interesting tidbits about mathematics. It is also a fantastic way to kill time when there’s too much grading to do.

We’re an Unofficial Blog of the Nazareth College Math Department in Rochester, New York and we welcome posts from people anywhere and everywhere. (Indeed, one of our most regular posters is a math professor from St. John Fisher College, the rival college down the road with a pretty cool math department itself!) Nazareth College itself is most assuredly not responsible for any content on here.

(Batman and Ξ  [Xi] are the folk from Nazareth (for email, you can reach Ξ by writing to “hlewis5”  @ “naz.edu” with the quotation marks and spaces removed.)

1. Graham Says:

All right, so I know one person at Nazareth, and one person at SJFC. What are the odds they’re the ones involved in this? (Smallish, I know.) If any of you are Matt K. or Erica J., hi there.

2. TwoPi Says:

What are those odds? Great question!

The Math Dept at Naz has five members, and two of them (Batman and Ξ) post here regularly; the Mathematical and Computing Sciences Dept at SJFC has (depending on how you count) nine mathematicians, one of whom (TwoPi) posts here regularly.

So if we pick one from each school at random, the probability that both of them post here regularly is $\frac{2}{5} \cdot \frac{1}{9} = \frac{2}{45}$, for odds of 43 to 2.

However, if we knew more information, those odds could be much higher. For example, if Graham had told us he knew one person at Naz and one person at SJFC because they had gone to the same graduate school, then we can narrow down the sample space from 45 pairs to just two pairs of people, the {MattK, EricaJ} pair that Graham asked about, and a second pair {Ξ, TwoPi}, leading to 1 to 1 odds.

3. Ξ Says:

Graham, you must be a Nebraska alum!

TwoPi posted the odds that both of your buddies post here regularly. In an abstract sense, the likelihood that you know at least one is
$1 - \frac{3}{5} \cdot \frac{8}{9} = \frac{21}{45}$
or odds of 24 to 21, so pretty close to 50-50. And indeed, while Batman is taking students to some math talks today, I know he’ll be happy to see your hello when he returns!

4. Batman Says:

At least one of us (indeed, at most one of us, too) is from UNL, and yes, you found me. So I’d say the odds are pretty good. Hiya!

5. Maria H. Andersen Says:

Can one of you guys send me an email about a collaboration project I will be working on during my sabbatical next year? I can’t find any email address for either of you on the blog.

You can delete this post … I just don’t know how else to get ahold of you.

Maria (wyandersen@gmail.com)

6. Ξ Says:

I just emailed you! 🙂 We try to keep the emails off here because of robo-spam (as opposed to being super-secretive), but my school is naz.edu and before the @ sign you’d write hlewis5.

7. Tam from Puntabulous Says:

Ξ, I got your card. 🙂 Can you e-mail me? I can’t seem to find your e-mail. We can discuss our shared ancestry. Have a great holiday.

8. Ξ Says:

Hi Tam! I emailed you, and also added my email (in a way probably not nearly hidden enough to avoid spam) to this About page. 🙂