Fill in the missing number:
π, 1, __, 3, 11, 15, 13, 17
Some people, when confronted with an artificial problem like this, simply throw up their hands. It's a trick, it's a waste of time, there's really no value in it.
Some people look for the quick insight, the fact that there's an irrational number, that the string doesn't go on forever, etc. But they usually get stuck.
Some people are only interested in the answer, and are eager to argue that it should be zero, not four, while others would point out that zero isn't necessarily a natural number, and on and on, merely as a way from hiding from the entire point of the lesson.
The real lesson happens once we realize the metaphor that's available to each of us: Things don't need to be artificial to be puzzles. In fact, if you're willing to be disappointed in your search for the right answer, just about every situation is a puzzle, a place where an insight might be found.
Artificial puzzles like this one generally guarantee a right answer exists. The challenge of the natural puzzle is that you eagerly accept that maybe, there's no good solution.
If you don't like the puzzle you've got, pick a different one. We're never going to run out of puzzles.
Our human interactions, the scarcity around us, the opportunities we all have—they're puzzles. They are invitations to find a new way to do something, a beneficial shortcut, a connection in an economy based on connections.
But first, you have to see.
[PS time to start planning for Thanksgiving.]