Tic Tac Toe 1

Logic Level 2

O 1 2 3 O 4 5 6 X \begin{array}{l|c|r}O & 1 & 2 \\ \hline 3 & O & 4 \\ \hline 5& 6 & X\end{array}

In the above position it's X turn. In which boxes if X puts his sign he'll lose?

Note: Assume that X and O are both trying to win. Write your answer as a sum. If it's impossible write 0.


For more of these check out the set Tic Tac Toe


The answer is 14.

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5 solutions

If X X puts his sign in either of the two ways shown above (the yellow X X is the move), he will force O O to block his three-in-a-row and the game will be a draw.

If X X puts his sign in any of the following positions, he will loose because O O can put his sign in a way that he can make a three-in-a-row no matter what could be X X 's third move:

In the image above the yellow X X represents X X 's second move and the rede O O represents O O 's third move. The red lines shows where O O will be able to make a three-in-a-row in his fourth move.

If X put in 1 , O can put in 3 or 5 and then O will in his next turn, because O will have 2 ways to win in this case.

It is symmetric , so also if X puts in 3 , X will lose .

If X put in 4 , O will put in 2 and then O will in his next turn, because O will have 2 ways to win in this case.

It is symmetric , so also if X puts in 6 , X will lose .

If X put in 2 , O will put in 4 then X will put in 3 then O will put in 1 or 6 to have an opporunity to win , then X will put in the other choice of "1 or 6" and then O will put in 5 (last box) so it is draw .

It is symmetric , so also if X puts in 5 the game will end as draw .

So the answer is 1+3+4+6=14

David Vreken
Dec 21, 2018

If X goes at 1, then O can go at 5, and O will win at either 2 or 3 on his next turn (whatever X does not block), so X will lose.

If X goes at 2, then O must block at 4, and then X must block at 3, and this will eventually result in a draw.

If X goes at 4, then O can go at 2 to block X's two in a row, and O will win at either 1 or 5 on his next turn (whatever X does not block), so X will lose.

By symmetry, if X goes at 3 it will be same result as X going at 1 (X will lose), if X goes at 5 it will be the same result as X going at 2 (a draw), and if X goes at 6 it will be the same result as X going at 4 (X will lose).

Therefore, X will lose if he goes at 1, 4, 3, and 6, and 1 + 3 + 4 + 6 = 14 .

V I S I O N .
Jan 9, 2019

X can only win if he places at 2 or 5 , at every other position O can win by forming two ways to win of which X can block only one

B D
Dec 23, 2018

If X X puts in 1, O O will put in 5 and has two chances to make 3 in a diagonal or column. X X loses .

If X X puts in 2, O O must put 4, then X X must put in 3, O O can put in 1, 5 and 6 . Lets say he puts in 1. X X must put in 6, O O puts in 5 and it is a draw.

If X X puts in 3, O O will put in 2 and has two chances to make 3 in a diagonal or row. X X loses .

If X X puts in 4, O O must put in 2 has two chances to make 3 in a diagonal or column. X X loses .

If X X puts in 5, O O must put in 6, X X must put in 1, O O can put in 2, 3 and 4. Lets say he puts in 3, X X must put in 4 and O O only has the space to put in 2. And it's a draw.

If X X puts in 6, O O must put in 5 and has two chances to make 3 in a diagonal or column. X X loses .

1 + 3 + 4 + 6 = 14

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