The First to Reach 15

Amy and Becky are playing a game. There are nine cards, numbered 1 to 9. The players take turns and pick up one card. The first player to pick up a set of three cards that add up to 15 wins the game. What is the strategy? 

The game’s objective is to create possible sets of 3 numbers that add up to 15. This can be achieved by building a 3 x 3 matrix as follows. 

So, Amy starts the game by picking one of the numbers, say 5. Let’s mark it by X. 

Becky then wants to complete a row or a diagonal, preventing Amy from doing so. She picks 6, denoted by O.

In other words, this game has become a tic-tac-toe, where a draw is also possible.

Game Theory Puzzle: The Race To 15: MindYourDecisions