Working through a neat logic puzzle from 1to9Puzzle

I saw a neat logic puzzle in my twitter feed last week:

Today I had the boys work through it.

Here’s the introduction to the puzzle and some of their initial thoughts:

Here’s their solution to the puzzle – it is really neat to see the thought process they go through to arrive at their answer:

Finally, there was a neat (and different!) solution posted on twitter and I asked the boys to see if they could understand the thinking behind this alternate solution: