Category Archives: Casting Out Nines

February 28, 2014, 11:15 am

Weekend reading (February 28)

This week’s small shiny objects from around the interwebs:

John Cook has an interesting short article on the log semiring. Suitable for nontrivial examples in your next ring theory class.

Here’s a terrific short video that explains the Diffie-Hellman key exchange in terms of color mixing.

Here’s a longer video of John Baez talking about network theory, which we first mentioned a few weeks ago.

And here’s a video by Stephen Wolfram giving an introduction to the Wolfram Language. I’m curious to try this out.

Just in time for the NFL Draft season (OK, it’s still six weeks away, but whatever) here’s an interesting article on how the Dallas Cowboys used statistics and computers to revolutionize their approach to tracking and choosing players. Consider it an early prototype of Big Data.

Are today’s tablet and phone apps turning us into sociopaths? It might be …

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December 29, 2013, 1:05 pm

4+1 Interview: Gavin LaRose

glrsign2After a bit of a hiatus, here is the newest installment in this Casting Out Nines’ series of 4+1 Interviews. In these interviews, I’ve tapped various people who are doing interesting work in some combination of math, technology, and education to see what they’re up to and what’s on their minds.

In this interview, I had a chance to catch up with Gavin LaRose. Gavin is affiliated with the Mathematics Department at the University of Michigan. He is officially listed as a Program Manager of Instructional Technology in the Mathematics Department, but his areas of interest and accomplishment are a lot more varied than what that title suggests. He’s been involved with Project NExT and other programs in the MAA and is well known for his work with innovative pedagogy and instruction, especially instruction using technology, at U-M. 

1. At the University of Michigan, you do some…

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December 17, 2013, 9:49 am

Back in the saddle

Well, it’s been a few weeks months since I last posted here. The blog is still alive and so am I. I had to put this blog on unintended, unannounced hiatus for a couple of reasons.

First, and I’m glad for this, Fall semester was a hugely busy time for my speaking and consulting activity. If you go back to August, this semester I gave eight presentations – three of those being intensive workshops on the inverted classroom, and one of which was a keynote presentation at the MichMATYC conference. I really enjoy doing this sort of thing but at one point in October I was averaging one of these a week, and these presentations aren’t quick to produce. I’ve complained in the past that the people who tend to see running around to education conferences and telling people how to be better teachers are not themselves in the classroom; now I understand why. There’s just no way you can…

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May 7, 2013, 7:33 pm

Guest post at DeltaScape: Does this make sense?

I lost a bet with my friend and colleague Dave Coffey (remember him?) over the NCAA mens’ basketball tournament, and as a result, I owed Dave a guest post on his blog DeltaScape. Risky move on his part, in my opinion, since his blog is a consistently excellent source of wisdom about math education and teacher training. I hope I didn’t mess it up too much — my guest post, entitled “Does this make sense?” is about so-called sense-making activities and what they mean for math instruction. It can be found here. Enjoy!

December 24, 2012, 3:34 pm

Merry Christmas

It’s not Thanksgiving, but during this season I’m very thankful:

  • For all of you who check in on this blog from time to time, who have it in your RSS feeds, and who add your comments.
  • For the Chronicle, for having the momentary lapse in judgment that led to me being part of the blog network since last fall.
  • For the Chronicle web development team, working behind the scenes to keep all these sites up and running.
  • For my online friends from Twitter and Google+ who interact with me these and give me a tiny slice of a tight budget of attention.

Being able to write about math, education, and technology here at Casting Out Nines is a great privilege. I’m humbled to be able to do it, and I’m looking forward to good conversations in 2013.

I’m taking the rest of this week off to hang out with my wife and kids and friends. In the meanwhile, enjoy Christmas. In my Christian faith…

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July 27, 2012, 9:25 am

Finding your next job: Understanding “why”

I’ll be at MathFest next week, and one of the things I’ll be doing is participating in this panel discussion. I’ll be speaking about “Finding Your Second Job” and then leading a breakout group to discuss this issue. It’s a little funny that I’ll be speaking on this, since I’m actually on my third job right now (and I hope it will be my last one!) but I won’t let that get in the way.

Finding “the next job” in academia is a very complex issue on a number of levels. I only have 15 minutes to do my schtick in Madison and so there’s no way I can touch on all the nuances. So I’d like to take this week leading up to MathFest to blog about this issue in detail. There may be some people out there who are planning to go on the market in the fall — or wrestling with the possibility of doing so. If you can make it to MathFest, I encourage you to stop by the panel…

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December 26, 2011, 6:33 pm

Merry Christmas, and a programming note

I want to wish all of you folks out there a Merry Christmas. (I know not all of you share my faith tradition, but allow me to wish it to you anyway.) I hope you have been able to enjoy the season, and if you’re in academia, I hope you’re enjoying the break between semesters.

I also just wanted to announce that I’ll be taking this week off from blogging and will resume posting on January 2. I’ll be heading out to Boston for the Joint Mathematics Meetingsat 6am on New Year’s Day and hope to do some blogging from the conference while I’m there. If you’re at the meetings, I hope you’ll consider attending my talk Making proofs click: Classroom response systems in transition-to-proof courses at 10am on Wednesday in the Back Bay Ballroom D, 2nd Floor of the Sheraton. I’ll also be attending the MAA minicourse on discrete and computational geometry prior to the meetings, so maybe I’ll see…

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September 20, 2011, 8:00 am

Flipping the college classroom

This Thursday (Sept 22) at 2:00 PM EDT, I’ll be giving a webinar for AMATYC called “Flipping the college classroom”. This is all about the flipped, or what I call the “inverted”, classroom — what it is, why it could be a better model for student learning, how it’s been implemented at the college level, and tools and strategies for flipping your own classroom. This is a subject near to my heart, as CO9′s readers know, and it’ll be fun to talk about it. It’ll be my first-ever webinar, and I think it’ll be an interesting experience, even as I pray for no massive tech screwups.

Although it’s an AMATYC event, registration is now open for the general public. Just click here and register yourself as a visitor.

September 19, 2011, 8:00 am

Math Monday: What is casting out nines?

http://www.flickr.com/photos/artnoose/

Last week in this post, I asked for requests for math topics you’d like to read about. One person wrote in and asked:

Why don’t you enlighten us about the name “Casting Out Nines?” I learned a system in grade school with the same name –it was a way of checking multiplication and long division answers. Long before calculators.

A review please?

OK then. Casting out nines is an old-fashioned method of checking for errors in basic arithmetic problems (addition and subtraction too, not just multiplication and division). Here’s how it works, using addition as an example.

Let’s suppose I’m trying to add 32189 to 87011. I get a sum of 119200. But did I make a mistake? Do the following to check:

  1. Take the first number, 32189, and remove — “cast out” — any 9′s…

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September 5, 2011, 2:06 pm

Welcome to Casting Out Nines

Greetings! I want to welcome everyone to the new digs for Casting Out Nines, my blog on math, education, and technology. This blog has been around since December 2005, but this is the first official post on this blog as part of the Chronicle of Higher Education blog network. All the old content has been (as far as I know) ported over to this new site, so you’re not missing anything by not going over to the old site.

I’m really pleased to join the blog network, and I look forward to some good conversations coming up.