[Phys-L] simple puzzle: drawing squares on a grid of dots

[John Denker <jsd@av8n.com>]

Here's an amusing little puzzle:
  https://www.av8n.com/physics/thinking.htm#sec-dots-squares

It's a bit of an "Aha!" problem:
 * Some students will find it ridiculously easy.
 * Some students will be completely stumped ... but when they
  see the solution they will agree in retrospect that it is 
  simple and obviously correct.

I mention it here because it might be useful on a placement test,
to assess problem-solving skills.