It's a math puzzle designed for third graders, but many adults are having trouble solving it. The puzzle looks something like Scrabble, with a series of boxes that snake up, down and across a page.

[Kagen Sound] is a woodworker and artist who gives a great behind-the-scenes look at his amazingly high-quality puzzle boxes (video). Not only do his varied puzzle box designs show his math background ...

Imagine that you have three boxes: one containing two black marbles, another containing two white marbles and a third containing one black marble and one white marble. The boxes were labeled for their ...