### Have You Got It?

Can you explain the strategy for winning this game with any target?

### Traffic Lights

The game uses a 3x3 square board. 2 players take turns to play, either placing a red on an empty square, or changing a red to orange, or orange to green. The player who forms 3 of 1 colour in a line wins.

### Yih or Luk Tsut K'i or Three Men's Morris

Some puzzles requiring no knowledge of knot theory, just a careful inspection of the patterns. A glimpse of the classification of knots and a little about prime knots, crossing numbers and knot arithmetic.

# Fifteen

##### Stage: 2 and 3 Challenge Level:

Fifteen is a game for two players that you can play anywhere, anytime. Try it without writing anything down. You take it in turns to choose one of the whole numbers 1 to 9 (and each number can only be chosen once). To win you have to pick 3 numbers that add up to 15.

Can you beat the computer?

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Click on a number to select it.

Can you analyse the structure in the following games and the correspondences between them? Describe the patterns that show they are equivalent games that can be played using equivalent strategies.

We suggest tackling them in the order given.