SNAP Mathfairs
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    • Level 1 Puzzles >
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    • Level 2 Puzzles >
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      • Abdication
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      • About the Solutions
    • River Crossing Puzzles >
      • The fox, the goose, and the grain
      • The fox, the goose, and the grain, and the dog
      • The mouse, the elephant, the dog, and the cat
      • Soldiers and children
      • Animal Crossing
      • The Three Thieves
      • The Missionaries and the Cannibals
      • Quarrelsome Boys
      • Jealous husbands
      • A Handful for the Farmer
      • The farmer, his children, and their pets
      • About the Solutions
    • Sudoku-Type Puzzles >
      • Cats, Cows, and Pigs
      • Latin Squares
      • Apple and Bananas I
      • Apple and Bananas II
      • Apple, Bananas, and Cherries
      • Four Skyscraper Puzzles
      • Colourful Cats and Pigs I
      • Colourful Cats and Pigs II
      • The Wizard's Hats
      • Four Colours
      • About the Solutions
    • Other Puzzles >
      • Catch the Thief
      • Cherry Glasses
      • Coin Jumping I
      • Coin Jumping II
      • Evensies
      • The 22 Game
      • Switch Positions
      • Spellbound Frogs
      • The Die Hard Jugs
      • About the Solutions
    • About the Solutions
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Quarrelsome Boys

A father took his sons out for a picnic and had to cross a river in a small boat. The boys were born one year apart. Two boys would fight each other if their ages differed by one year, provided that the father was not around to stop it.

Given that only the father could row, how could this family cross the river peacefully, if

there were three boys and the boat held two people;
there were five boys and the boat held three people, and the father could stop fights on the boat;
there were five boys and the boat held three people, but the father could not stop fights on the boat?
(From T. H. O'Beirne's Puzzles and Paradoxes.)