This is great, can't wait to try it with a class
Great! You could even have the students make their own puzzles to challenge each other. If you do, let me know, and I'll post them!
In the top right puzzle, the one that starts with a 15, could the bottom right number (4) be substituted for a 56? (Or for that matter, any number that is the product of 2, 4, and a prime?)
Yes, you're right that 56 would work - in fact any number that is a multiple of 4 but not also a multiple of 5 would work. The only issue is that there is a restriction stated in the problem that the numbers be between 1 and 20. Thanks for your input!
Wow, I totally overlooked that restriction. Thanks!