Topics: Starter | Combinations | Puzzles

• Transum,
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• Another game which is isomorphic (same strategies) to noughts and crosses is the game of Fifteen. The numbers 1 to 9 are written on cards. Players take it in turns to take a card. The first person who can make a total of 15 with the cards they have is the winner.
  If you arrange the nine numbered cards to form a magic square you will see the similarities with noughts and crosses.
  We have invented a game called Trilett. Play it a few times and see if you can work out why it is isomorphic to noughts and crosses.
  
  Here are links to the related interactive activities:
  
  Noughts and Crosses | Fifteen | Trilett
• Miss Mears, Stockport
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• A nice starter - we then extended the idea to the general case of an nxn grid and used some algebra as well.
• Mark, New Zealand
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• Surely there are only three ways that the first cross can be placed: centre, side or corner. In any meaningful analysis of the game the sides are all identical and should not be distinguished.
• Mrs. S. Farragonda, Fernan Elementary, CDA, ID
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• This game is very mental, and fun for both teachers and students! We now do the "secret student" thing with our class laptops. If the secret student is playing and X wins, the class wins. So everybody is motivated to do well.
  
  [Transum: There's no better way to select a 'secret student' than to use the Random Student Generator.]
• Transum,
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• Tired of the usual noughts and crosses? Why not mix things up with an interesting twist? In this variation, the basic rules remain the same, but with one key difference: each player can choose whether to place an X or an O on their turn. That’s right - you can switch between X and O as you wish. One turn you might play X, and the next you might choose O, or you can stick with the same symbol if you prefer. The goal remains the same: be the first to line up three of the same symbols in a row to win.
  
  I heard about this variation called "naughty naughts and crosses" in a book by John Driscoll called A Hen and a Half, Intriguing Conundrums, Confusing Paradoxes, Baffling Conjectures and Challenging Puzzles.
• Team Fortress 2 Soldier, Valve Studio (not The Real Valve Of Course)
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• Me and my friends loved this game, it's quite fun and relaxing, it would be amazing if you could play this on a long car trip but there is no internet on the road sadly.
  overall great game.

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