Maths Challenge
Maths challenge.net: Painted Faces
Mathchallenge offers this mathematical reasoning problem, a one star problem requiring nothing more than a logical mind and paper and pencil, to deduct the painted faces problem
San Jose State University
San Jose State University: Categorical Fun
Six logical problems are defined to challenge students to use critical thinking skills as they tackle these brain-teasers. No answers are provided, but there are some instructions for how to approach the problems.