Question 3
There are 70 balls. Peter and Mary alternately take 4 to 8 balls. The person who takes the last ball wins. Peter moves first and may add balls before play. What is the least number he must add to guarantee victory?
Editorial reading of the printed last-ball rule: every move must take 4–8 balls. If 1–3 remain, no legal move is possible and neither player has taken the last ball; being unable to move is not itself a win for the other player.
Editorial reading of the printed last-ball rule: every move must take 4–8 balls. If 1–3 remain, no legal move is possible and neither player has taken the last ball; being unable to move is not itself a win for the other player.