Here are some mathematical puzzles that I have enjoyed. Most of them are of the kind that you can discuss and solve at a dinner table, usually without pen and paper. So as not to spoil your fun, no solutions are given on this page, but for some problems I have provided some hints.
- Half the area of an L
- A game of 2014 cards
- Evaluating a polynomial
- Picking the larger of two cards
- Enclosing land by fence pieces
- Finding a restaurant in a park
- Handshakes at a dinner party
- Planar configuration of straight connecting lines
- Car and key hide-and-seek
- Transporting bananas
- Reducing nearby enemies
- Rectifying a pill mistake
- Alternating T-shirt colors
- Chomp
- Digit sums of multiples of 11
- Weighing piles of coins
- Guessing each other's coins
- The duck and the fox
- 3-person duel
- Age of children
- Capturing a pirate ship
- Dropping eggs
- Finding a hermit
- The genders of the neighboring family's children
- A special squarish age
- Average clan size
- Boris and Natasha
- Burning ropes to measure time
- Catching a spy
- Children and light switches
- Coins in a line
- Colored balls in boxes
- Cutting cheese
- Determining a hidden digit
- Determining the number of one hat
- Dropping 9-terms from the harmonic series
- Fair soccer championship
- Finding a counterfeit coin
- Flipping cards
- Frugal selection of weights to weigh a thing
- Initializing an array in constant time
- Knight, knave, commoner
- Lemmings on a ledge
- Making a square larger
- Mixed up airplane seats
- Mixing vinegar and oil
- Multiples in the Fibonacci series
- Opening boxes in a prison courtyard
- Passing alternating numbers of coins around
- Path on the surface of the Earth
- Placing coins on a table
- Points on a circle
- Poisoned wine
- Psycho killer
- Random point in a circle
- Right triangle with a 23
- Stabilizing nodes from an anchor
- Subsequence of coin tosses
- Summing pairs of numbers to primes
- Table with four coins
- The electrician problem
- The exact batting average
- The hidden card
- The line of persons with hats
- The prisoners and the switch
- The worm and the rubber band
- Three hat colors
- Translation error in a cookbook
- Voting on how to distribute coins
- Witches at a coffee shop