The students above are tackling Costas arrays. The details surrounding Costas Arrays are not important. What is important is that finding a Costas array of a certain size is difficult, but that once an attempt at a solution is shown to you, it is pretty easy for you to say if it is a FAILURE or a SUCCESS.
Mathematicians call these NP problems.
When I’m designing puzzles for the elementary school math classroom I’m purposely trying to design NP problems. I expect most of the puzzles that I call Infinite Pickles (see the book “The Infinite Pickle“) are NP problems. There are pedagogic benefits for introducing problems like these in the classroom. They help engage the full spectrum of students. Struggling students can work on skill aquisition while top students are deflected into problem solving (never a waste of time.)
Please continue designing puzzles like this. 😉