[ Sorry for the delay in announcing the winner. I ran into a technical issue that I needed to get resolved.]
On November 1st I announced a contest. Folks entering the contest were eligible to win if they correctly solved a Math problem of my choosing. The prize was a TI-84 calculator, graciously donated by Texas Instruments.
Random.org selected Nate Burchell as our winner. We had 20 submissions. Almost all of them were correct.
I sometimes post a solution other than the winner's because sometimes the winner's solution, while correct and well explained, is not the best example of how to solve a problem. In this case, though, Nate explained his solution quite well.
Here is Nate's solution.
Nate is a Math teacher and blogs at http://burchellmath.blogspot.com.
Thanks to everyone who played. Stay tuned for another puzzle or three in the coming weeks.