22
@hexomino's answer is correct and well-reasoned, as always. Here's another approach, which to me feels much more.. "axe-to-the-head" is what I'd call it in my native language, so I thought it might be interesting enough to warrant posting.
Lower bound: (This is what @trolley813's encrypted comment is saying.)
Upper bound:
9
I think the answer is
Reasoning
As trolley813 mentions in the comments
6
Short way to guess at the answer:
Proving that this works:
Now you asked about strategy:
3
Using a modified version of Albert Lang's method on the previous question, the best I've managed so far is
As follows
3
Here is a solution with six lines:
It's difficult to tell how I found this, except that I already knew a solution for a 3 by 3 grid with 4 lines, which can be found e.g. here on our sister site Mathematics Stack Exchange. It's also possible that a solution with 5 lines exists.
(By the way, the puzzle is missing the requirement that the lines must be ...
1
It feels like this can be improved but the best I've been able to do so far is
As follows
1
I don't know if this satisfies the intended problem but it follows the rules. I approached it by looking at the minimum multiple choice answer, and trying to exclude solutions of that size.
Only top voted, non community-wiki answers of a minimum length are eligible
