When does one plus one equal three? This is the kind of math that can make a preschooler scratch her head, and an excellent demonstration that sometimes there are other forces at work - in this case the physics behind balancing on a seesaw. But kids don't need to understand either the physics, or the math because just playing is the best way to solve these seesaw puzzles. And these puzzles are so much more than an academic exercise because it's not just about balancing the board, you have to balance it using the pieces specified on the challenge cads - and that's the real puzzle. A totally fabulous set of challenges for young minds.