You know this one, but I have a new twist on it….
Without lifting your pen from the paper, draw 4 straight lines which go through each of the nine dots exactly once.
When you first came across the problem you were probably foxed, at least for a while. Then you either noticed, or were told, the unspoken assumption that was holding you back. You assumed that the lines had to stay inside the nine dots. Once you realised that this was nowhere stated in the problem, the answer became simple:
Literally, the answer comes from going “outside the box.”
So far, so familiar. But …there is a simpler solution. You can in fact join all the dots with only 3 lines. Give it some thought. The solution is here.