You have a student who is trying to solve a 3×3 magic square. She’s been trying for a week, and keeps getting it almost to work: usually she gets to 6 directions out of 8 that add to 15, the other two add to 12 and 18. She keeps wanting to give up and keeps asking for help. So far you’ve just told her to keep going, and she has, but her near-misses are starting to repeat themselves, and she’s getting bored.

What should I do you tell her to aid her investigation without taking it away from her? In other words, help her out, possibly making the problem simpler, without giving an answer or algorithm.

No deadline, but answers arriving before Monday will be more likely to have real-world impact.