I just picked up my September/October 2009 issue of Neurology Now, turned to page 13, and saw your “Sum Snap” puzzle. Challenge #2 asks, “How many chains of same-colored circles can you find that add up to 10?” My answer was five, but when I turned to page 14, I saw that the answer was supposed to be four. In fact, I was correct: There are three chains of circles colored green that add up to 10. The answer sheet correctly identified the chains 5-3-2 and 3-2-1-4. I found these as well; however, the green circle chain 1-4-5 wasn't identified.
Kevin Pettit, Ph.D.