Problems

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In each square of an \(11\times 11\) board there is a checker. Consider the game with two players where: in one move a player is allowed to take any amount of adjacent checkers from the board, as long as they checkers are in the same vertical column or in the same horizontal row. The winner is the player who removes the last checker. Which player wins the game?

There are two piles of rocks: one with 30 rocks and the other with 20 rocks. In one turn a player is allowed to take any number of rocks but only from one of the piles. The loser is the player who has no rocks left to take. Who would win in a two player game, if the right strategy is used?

There are twenty dots distributed along the circumference of circle. Consider the game with two players where: in one move a player is allowed to connect any two of the dots with a chord (aline going through the inside of the circle), as long as the chord does not intersect those previously drawn. The loser is the one who cannot make a move. Which player wins?

In the first pile there are 100 sweets and in the second there are 200. Consider the game with two players where: in one turn a player can take any amount of sweets from one of the piles. The winner is the one who takes the last sweet. Which player would win by using the correct strategy?

Two players in turn put coins on a round table, in such a way that they do not overlap. The player who can not make a move loses.

Two people play the following game. Each player in turn rubs out 9 numbers (at his choice) from the sequence \(1, 2, \dots , 100, 101\). After eleven such deletions, 2 numbers will remain. The first player is awarded so many points, as is the difference between these remaining numbers. Prove that the first player can always score at least 55 points, no matter how played the second.