Four in a row
Where should black play in this game of four-in-a-row to be certain of winning on her next move?
Age
11 to 14
Challenge level
Problem
In the game Four-in-a-Row, two players take it in turns to place counters on the $5 \times 5$ board. The winner is the first player to have $4$ adjacent counters in a line across or down (but not diagonally).
It is Black's turn to play next. Where should she play her fourth counter to be certain of winning on her fifth turn whatever White plays?
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If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
Student Solutions
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X marks the spot!
If black plays here, wherever white plays, black will be able to play in one of the bottom corners, completing a row of 4 along the bottom.