2012 Free Budgeting Spreadsheet and Expense Tracker
I just wanted to let everyone know I have uploaded the newest spreadsheet (can be downloaded here) The only substantive change I made from the 2011 spreadsheet was to add a column for per diem budgeting (though technically that was a mid-year change I introduced in August written up here) The only ...

Best of Mind Your Decisions 2011
I posted a lot more this year than in others, so I figured it would be fitting to have a recap of the year's best posts. Here are some posts from 2011 that you might have missed and are worth a second look. Most of them are puzzles, which happened to ...

Expense tracking: end of year review
For 4 years on this blog, I have been praising the benefits of tracking expenses (get the free spreadsheet here). I have gone into detail on how best to account for purchases properly, including topics such as: Tracking expenses while traveling How many categories should you have? Why the richest American suggested tracking expenses But I ...

Video: strategy in a TV game show
Game theory concepts can often help when trying to win prizes on a TV game show. I have previously written about a couple of the scenarios from the U.S. show The Price is Right: Optimal strategy in spinning the wheel Strategy for Pay the Rent Strictly dominated strategies in Lucky Seven I came across ...

Puzzle: ant and honey
The shortest distance between two points on a plane is a straight line. But finding the shortest distance on other surfaces is a more interesting problem. Here is a puzzle that is harder than it sounds:

Video: Braess Paradox demonstrated with springs
A couple years ago, a few roads in my town were closed due to flooding. I was at first worried the road closures would make roads congested. But to my surprise, traffic seemed to be moving faster. Why was that?

A gift puzzle
With Christmas around the corner, I thought this puzzle would be appropriate. This is a nice problem that I found in a math puzzle book.

Optimal shaving frequency
This week has already featured two puzzles about optimizing (Christmas trinket puzzle, auction theory puzzle), so I thought I'd keep the trend going today. Today's post is actually inspired by a problem I considered when I shave my head. Here is the story and my results.

Auction theory puzzle: finding the right number of bidders
If you liked yesterday's puzzle about optimizing with uncertain demand, you'll definitely enjoy today's post. One of my favorite topics related to game theory is the subject of auction theory. The results from auction theory are very interesting, but I have yet to cover much about it because the math can be ...

Puzzle: how many Christmas trinkets to buy?
I came across a very interesting problem in the math section of reddit. The problem is about a business that wants to decide how much inventory of a product to buy facing an uncertain demand. The business wants enough to maximize profits, but it knows that unsold units will be ...

Poll results: debit card use
A couple months ago I asked readers of this site how frequently they used debit cards, if at all. Here are the poll results:

Video: the “hardest” geometry problem in the world
Rushmore is a rather quirky but interesting movie that came out in 1998. One of the scenes I particularly enjoyed is about the main character doing a mathematical proof. During class, Max Fischer asks the teacher about a math problem written on the board. The teacher explains the problem is a joke: ...

Holiday expense tracking
The holiday season is a special time. But however you enjoy the holidays, it is important not to forget about your finances. All those gifts and donations do add up, and you will want to keep a consistent record of your spending. Here are a few examples of holiday purchases and some ...

Cannibal game theory – a cool math puzzle
I came across a really interesting game theory problem at David Cowan's blog. The problem not only is about strategy, but its proof is interesting mathematically too. Here is the puzzle:

Puzzle: random size confetti
Today's puzzle is about statistical sampling, adapted from a problem I found in this book. Professor X teaches a probability class. He assigns a holiday-themed project to his students.