# Answer to the Friday Puzzle….

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On Friday I posted this puzzle….

Can you place six X’s on this naughts and crosses board without making three-in-a-row in any direction?

If you have not tried to solve it, have a go now.  For everyone else the answer is after the break.
Here we go…
Did you solve it?
I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.

1. Geodetective says:

Yes, that was my solution.

2. Richard says:

I got it (and obviously the 90 degree rotation) but it took ages of randomly adding 2 crosses to each row until I occidentally stumbled on the right answer.

I wonder if there’s any sort of logical way to do it beyond “brute force” ?

• Lazy T says:

Not putting X in the middle square seemed logical to me.

• ivan says:

With 6 crosses to fit in, clearly there has to be 2 in each row. There are only 3 ways to put two crosses in a row, so that leaves a maximum of 9 options to test, and some of those disappear due to symmetry, etc, so not many options to check.

3. Anne Elk says:

This is the answer I got. Simple but still fun.

4. Anne Nicklen says:

I put them all in two boxes – no straight lines!

• The other Matt says:

Me too, because i didnt start to try the normal way.

5. Alma says:

This one was too easy. Even for me. 🙂

6. Eddie says:

Why the thick crosses? A bit over the top.

• Anonymous says:

Why not?

• Mary says:

Is it a hobby of yours to complain about pointless things that have no affect on you?

• Eddie says:

If they had no effect on me I wouldn’t complain about them.

• Mary says:

Well then maybe you should get a life.

• Anonymous says:

Love you too, Mary.

7. churchynet says:

I flipped the question and looked for three bought to block the game. Made it a bit easier…

8. Kristian says:

There was no restriction of “1 cross per cell”, so I just put multiple small crosses inside the same cells. Felt a bit naught-y though.

9. Miss Chili says:

10. Fotoflex says:

Got it on the second try. Happy the have solved one for a change. 🙂

11. slugsie says:

Given that there were no mentioned restrictions on how you could place the Xs, I just put them all on one place.

I did also get the official answer.

12. Jaleel Hamid says:

I dit indeed! 🙂

13. mittfh says:

I wonder if you could extrapolate this to filling (n^2)-n squares in any grid of size n – and if there’d always be just one solution (plus rotations) or if there’d be multiple solutions with larger grid sizes (and if so, if the number of solutions could be determined algebraically)?

• ChrisR says:

you’ve always got a diagonal solution at least

14. issahamati says:

nice

I arrived at this answer (mirror image) in less than 10 secs. Then I thought “Where’s the trap”? Obviously 0 can win through the diagonal – so there IS a winner; so there must be a more devious solution, where there is no winner. Next I thought “Hold on. X can never place more than 5 Xs in any game”. So I gave up looking for a smart answer and moved on. Very disappointed.

16. Anonymous says:

i put all the X’s in the middle box. I thought that would count. I guess not. Good puzzle though.

17. Niva says:

How could anyone not get this in a nanosecond? I got this right away, but I thought maybe there’s a a better trickier answer. I reckon not.

• Cathy says:

sleep deprivation

18. Henry says:

Richard, Richard, Richard — the rigors imposed by promising a new puzzler every week must be enormous. My sympathies.This week’s challenge took roughly 3 seconds to solve after I finished reading it.

19. edje says:

hey man vet blog