**Math Puzzles / Contests at Williams**

**Lots of opportunities for math puzzles and contests, including**

- Weekly Math Puzzle Night Dinners
- Monthly Math Conundrums (first one below)
- The Putnam Exam (early December — cash prizes!)
- The Green Chicken Contest (at Middlebury this year)
- Mathematical Contest in Modeling
- Project Euler

Contact Professors Miller ([email protected]) and Stoiciu ([email protected]) to be added to the email list for updates.

**1 ^{st} Conundrum: Math/Stats is Infectuous**

The following is a standard problem, rephrased. Consider an n x n grid (so there are n^{2} squares). Color people purple if they’re a math/stats major, and (a sad) blue otherwise. Once you’re a math/stats major, you stay a math/stats major. If your square borders two math/stats majors, you become a math/stats major. In the picture below, in the next turn three people join the major, in the turn after that 1 more, then 1 more the next time, after which our major stops growing. Prove that if we start with n-1 majors, no matter how cleverly we place them, there will always be at least one person who doesn’t major in math/stats; however, prove that if we start with n math majors then it ** is** possible to place them in such a way that everyone ends up joining the major!