Current Problem | |

June 1, 2010 | A Set of Triangles |

June 22, 2009 | Third Grade Puzzles |

June 15, 2009 | Tetromonio Tiling |

June 5, 2009 | Which Coins? |

April 10, 2009 | Square Root of a Line |

February 6, 2009 | Magic Snowflake |

January 30, 2009 | Unique 8x8 Paths |

January 6, 2009 | Lines for Squares |

December 16, 2008 | Talisman Squares |

December 9, 2008 | Slow Cows |

November 10, 2008 | Coloring a Chessboard |

October 14, 2008 | Bob's New House |

October 7, 2008 | Daisy Chains |

September 24, 2008 | Traveling a Latin Square |

September 12, 2008 | Dividing a Square |

August 27, 2008 | Sum Pyramid |

August 7, 2008 | Nine Digits in Sums |

August 2, 2008 | More Knight Swapping % |

July 26, 2008 | Unique 5x5 Paths |

July 5, 2008 | Fill in the Blanks |

June 6, 2008 | Sums with 1 to 9 |

May 23, 2008 | Magic Pyramid |

April 16, 2008 | Calendar Fractions |

March 26, 2008 | Crossing a River |

January 26, 2008 | Latin and Euler Squares with Diagonals |

January 11, 2008 | Non-Sum-able Sets |

December 19, 2007 | Central Tendency |

November 12, 2007 | Cards in Order |

October 22, 2007 | Wires and Rooms |

October 12, 2007 | Sequential Digits on a Clock |

October 5, 2007 | Eight Magic Lines |

September 27, 2007 | Triangle and Rectangle Pairs + |

September 20, 2007 | Rods in a Mobile |

September 13, 2007 | Rods in a Box % |

September 6, 2007 | Circle Around Circles |

September 4, 2007 | Lacing (Short) Shoes |

August 27, 2007 | Hexagon in a Square |

August 20, 2007 | Equality on a Star |

August 9, 2007 | Digits in the Blanks |

July 17, 2007 | Patterns of Circles in a Grid |

June 18, 2007 | Circle in a Cube |

May 18, 2007 | A Hidden Hexagon |

March 26, 2007 | Attacking a Chessboard |

March 5, 2007 | Hiding in a Forest |

February 13, 2007 | More Balls and Urns |

February 2, 2007 | Inverted Addition |

January 26, 2007 | Unique 3x3 Grids |

January 5, 2007 | Sudoku Through A Cube |

December 29, 2006 | Swapping Knights Again |

December 19, 2006 | A Bet on a Card Deck |

December 12, 2006 | Counting on a Clock |

November 30, 2006 | Dots and Squares |

November 3, 2006 | Unique 2x2 Squares |

October 2, 2006 | Pieces of a Latin Square |

September 15, 2006 | Matching Numbers and Letters |

September 5, 2006 | Sinking a Cup |

August 24, 2006 | Checking the Doors |

July 31, 2006 | No Repeated Difference |

July 11, 2006 | Lighting An Icosahedron |

June 13, 2006 | Lines Through Dots |

May 16, 2006 | Seeing Digits % |

April 13, 2006 | No Repeated Sum |

March 24, 2006 | Card Magic Square |

March 9, 2006 | Mini Sudoku |

February 7, 2006 | Card Square |

January 28, 2006 | Successive Digit Division |

December 7, 2005 | Latin Square Puzzle #2 |

November 11, 2005 | 4x4 Peg Solitaire |

October 31, 2005 | Latin Square Puzzle |

October 24, 2005 | Left-Handed Times |

October 11, 2005 | Calendar Magic Squares |

September 29, 2005 | Cube Nets on a Grid |

September 2, 2005 | Division by 7 |

August 24, 2005 | Balancing Cards |

August 1, 2005 | An Average Age |

July 27, 2005 | Maximum Cross-Sums |

July 15, 2005 | More 10-Digit Numbers |

July 7, 2005 | Passing on a Track |

June 8, 2005 | Dividing Binary by Five |

May 31, 2005 | Safe Chess Pieces |

May 23, 2005 | Fifth Friday of the Month |

March 28, 2005 | Consecutive Additions |

March 21, 2005 | When to Enter? |

March 4, 2005 | 9-Digit Numbers |

February 28, 2005 | Routes on a Cube |

January 31, 2005 | Multi-Color Rectangles % |

January 21, 2005 | Fibonacci Dials |

January 10, 2005 | Parity Tic-Tac-Toe |

December 22, 2004 | Packing Digits |

December 13, 2004 | Fraction of a Can |

November 24, 2004 | Another Magic Hexagon |

November 4, 2004 | Finding Five Numbers |

October 21, 2004 | Minesweeper Puzzle |

October 11, 2004 | Minesweeper Chess |

October 4, 2004 | Rotated Multiples |

September 27, 2004 | Reversed Checks |

September 20, 2004 | Sums in a Grid |

September 13, 2004 | Combination Cracking |

August 16, 2004 | More Olympic Ring Addition |

July 23, 2004 | Folding a Square |

July 14, 2004 | Random Crayons |

June 29, 2004 | Product Pairs |

June 4, 2004 | Multiple Lowest Common Multiples % |

May 14, 2004 | Monty Hall Marathon |

May 7, 2004 | Minesweeper All Digits |

April 16, 2004 | Dominos One-by-One % |

March 23, 2004 | Dividing by Dropping Digits |

February 10, 2004 | Revisiting a Sangaku Problem |

January 6, 2004 | A Triangle from Three Sticks |

December 8, 2003 | Points in a Circle |

November 24, 2003 | Some Chessboard Problems |

October 31, 2003 | Right Triangles in a Square |

October 15, 2003 | Minesweeper Queens |

October 8, 2003 | Magic Octagon |

October 1, 2003 | Small Cubes in a Cube |

September 24, 2003 | Y in a Cube |

September 18, 2003 | A Broken Clock Face |

September 10, 2003 | Four Egyptian Fractions |

August 29, 2003 | Angles in a Pyramid |

August 22, 2003 | Magic Triangles in a Hexagon |

August 11, 2003 | A Rectangle and a Triangle |

August 5, 2003 | A Square, a Rectangle and a Triangle |

July 28, 2003 | A Domino Overhang + |

July 21, 2003 | The Length of a Rectangle |

July 14, 2003 | A Row of Card Pairs |

June 20, 2003 | A Deduction Problem |

June 3, 2003 | Two Exams |

May 14, 2003 | Difference Payoff |

May 2, 2003 | Do They Intersect? |

April 21, 2003 | Most Ridiculous Routes |

April 7, 2003 | Number Chain |

March 27, 2003 | Another Domino Magic Square |

March 19, 2003 | Roman Number Lengths |

March 4, 2003 | Escorting Shapes |

February 21, 2003 | Testing Three Students |

February 12, 2003 | Hiding Five Colors |

January 10, 2003 | Dissecting to Five Rectangles |

December 11, 2002 | Ten Digits and Two Squares |

December 11, 2002 | A's & B's |

November 20, 2002 | 1010101 to 950 |

October 23, 2002 | Three Unique Primes |

October 7, 2002 | Submissions & Requests |

September 16, 2002 | A Queen, 4 Kings, and 2 Rooks |

August 15, 2002 | Card Orders |

August 9, 2002 | Multiples of 7 |

July 25, 2002 | Black Box Paths |

July 4, 2002 | Flipping a Hemisphere |

July 2, 2002 | World Cup Direct Qualifying |

June 7, 2002 | Best of Seven |

May 29, 2002 | Two Blackjacks |

May 7, 2002 | More Letter Boxes |

April 25, 2002 | A Magic Pentagon |

April 17, 2002 | A Belt Around Two Pulleys |

April 6, 2002 | A Line in a Pentagon |

March 29, 2002 | Swapping Knights and Bishops + |

March 9, 2002 | Twelve Knights |

February 14, 2002 | A Sangaku Problem |

January 28, 2002 | Diagonal of a Pentagon |

January 3, 2002 | Series of Reversed Differences |

December 14, 2001 | Dividing Rotated Numbers |

November 30, 2001 | Common Sums in a Hexagon |

November 21, 2001 | Nine Digits Sum |

November 9, 2001 | Another Isosceles Triangle |

November 2, 2001 | A Six Degree Polynomial |

October 22, 2001 | Five Triangles in a Square |

October 15, 2001 | Power Cycles |

October 3, 2001 | Balancing Rods |

September 25, 2001 | Pirate Portions |

September 13, 2001 | Division of Powers |

August 29, 2001 | Coins on a Jar |

August 21, 2001 | Feet Per Minute |

August 14, 2001 | Chord Lines |

August 6, 2001 | Circular Tracks |

July 25, 2001 | An Inverted Magic Square |

July 17, 2001 | Pedals on a Bicycle |

July 10, 2001 | Pentagon in a Square |

June 26, 2001 | Equal Sums on a Circle |

June 16, 2001 | A 6-Digit Number |

June 1, 2001 | The Order of Lines |

May 16, 2001 | Two Scarecrows |

May 7, 2001 | Triangular Numbers and a Sequence |

May 2, 2001 | Magic Product Squares |

April 13, 2001 | Letter Boxes |

April 6, 2001 | 24 Knight Swap |

March 27, 2001 | A Six-Color Square |

March 20, 2001 | Arranging Numbers |

March 13, 2001 | A Third Cousin of Nim |

February 26, 2001 | A Sequential Magic Square |

February 15, 2001 | A Square and New Dice |

February 2, 2001 | Another Six-Pointed Star |

January 9, 2001 | A Lego Angle |

December 20, 2000 | Circles on a Line |

December 1, 2000 | Ordered Fractions |

November 21, 2000 | A Magic Hexagon |

November 13, 2000 | Reversed Differences |

October 30, 2000 | A Planar Circuit |

October 18, 2000 | Areas of Hexagons |

September 29, 2000 | More Partially Magic Squares |

September 18, 2000 | Partially Magic Squares |

September 4, 2000 | Letter Lines |

August 17, 2000 | A Diagonal of Two Squares % |

August 11, 2000 | Another Obedient Ray |

July 28, 2000 | Unique Rectangles |

July 13, 2000 | An Eight-Pointed Star |

July 6, 2000 | Right Triangles in a Square |

June 28, 2000 | Doubly Attacking Queens % |

June 14, 2000 | Ball Drop |

June 2, 2000 | A Triangle and Two Circles |

May 26, 2000 | Sorting Without Comparison |

May 12, 2000 | Packing Circles |

May 4, 2000 | 3x3 Magic Squares |

April 28, 2000 | The Spinning Egg |

April 20, 2000 | Identity by Ordered Subtraction |

April 14, 2000 | Colored Squares and Cubes |

April 3, 2000 | Reflecting Angles |

March 16, 2000 | Five Coins |

February 28, 2000 | Pairs of Socks |

February 15, 2000 | Close Divisors |

February 7, 2000 | Multiple Sums |

January 21, 2000 | How Many Marbles? |

January 12, 2000 | Quartominos |

December 24, 1999 | The Length of Memory % |

December 13, 1999 | Sums on a Triangle and Tetrahedron % |

December 3, 1999 | Coloring a Cube |

November 22, 1999 | An Equal Rectangle and Triangle |

November 15, 1999 | Greatest Common Divisors |

November 7, 1999 | The Path of a Billiard Ball |

October 29, 1999 | Triangle Perimters and Areas |

October 22, 1999 | Least Difference and MIMU |

October 15, 1999 | Rectangle Perimters and Areas |

October 5, 1999 | Five Queens |

September 24, 1999 | Two Lengths |

September 17, 1999 | Vanishing Triangles |

September 11, 1999 | A Six-Pointed Star |

September 6, 1999 | Vanishing Squares |

August 27, 1999 | Sum Less Than N |

August 20, 1999 | A Parking Problem |

August 13, 1999 | Magic Difference Square |

August 6, 1999 | Trigons |

July 30, 1999 | Points and Triangles on a Circle |

July 27, 1999 | Two Milkmen of Sam Loyd |

July 20, 1999 | A Domino Chain of Sums |

July 8, 1999 | Intersecting Square and Triangle |

July 2, 1999 | Continued Multiples |

June 25, 1999 | Two Islands |

June 18, 1999 | Egyptian Fractions |

June 11, 1999 | Mirror Multiples |

June 4, 1999 | Two Detectives % |

May 28, 1999 | Tetrahedrons |

May 21, 1999 | A Triangle and a Circle |

May 14, 1999 | Another Cousin of Nim |

May 7, 1999 | House Plaques |

April 30, 1999 | Square Division |

April 23, 1999 | The Trusses of Hay |

April 16, 1999 | Cards for Dice |

April 10, 1999 | 12 Counters on a Clock |

April 1, 1999 | Dry Gulch Treasure |

March 26, 1999 | 24 Coins |

March 19, 1999 | Cousin of Nim |

March 8, 1999 | APPLE+LEMON=BANANA |

February 23, 1999 | Fold-Points |

February 10, 1999 | Points on a Circle |

February 3, 1999 | Productive Moving Digits |

January 25, 1999 | Nine Bottles |

January 19, 1999 | More Rows of Checkers |

January 11, 1999 | 20-Sided Dice |

January 4, 1999 | Dog Crossing |

December 21, 1998 | Common Letters |

December 14, 1998 | Adjacent Sums % |

December 7, 1998 | The Centrifuge |

December 1, 1998 | Angles in an Isosceles Triangle |

November 20, 1998 | Square with a Compass |

November 13, 1998 | Square in a Pentagon |

November 5, 1998 | Sum to Squares |

October 26, 1998 | Perfect Powers Square |

October 16, 1998 | Two Ropes |

October 7, 1998 | Two Triangles |

September 23, 1998 | ONE+TWO+FOUR=SEVEN |

September 17, 1998 | Determining Altitude |

September 9, 1998 | 1998, Part 2 % |

September 2, 1998 | 1998, Part 1 |

August 26, 1998 | Unique Pairs and a Domino Square |

August 19, 1998 | Four Bits Square |

August 11, 1998 | Interlocking Circles |

August 3, 1998 | The Necklace Problem |

July 27, 1998 | Birthday Triangles |

July 20, 1998 | Alexander's Knight Puzzle + |

July 13, 1998 | Bob's New House |

July 6, 1998 | Queen's Quadrille |

June 29, 1998 | Domino Cross |

June 22, 1998 | Chocolate Bunnies |

June 15, 1998 | Deterministic Checkers * |

June 8, 1998 | Self-Referential Puzzles |

May 13, 1998 | The Empty Bottle |

May 5, 1998 | The Matching Car |

April 24, 1998 | Ten Pentominos in Two Squares |

April 15, 1998 | Couples in a Candy Store |

April 7, 1998 | More than Three Polygons |

March 31, 1998 | More Sums on a Triangle |

March 23, 1998 | The Monkey and the Coconuts |

March 12, 1998 | Dividing a Triangle |

March 5, 1998 | Primes on a Clock |

February 25, 1998 | Bisection in a Triangle |

February 17, 1998 | Balls and Urns |

February 10, 1998 | Equal Areas |

February 2, 1998 | More Rounded Corners |

January 26, 1998 | Rounded Corners |

January 21, 1998 | A Few Final Sums |

January 13, 1998 | Sums on a Triangle |

January 5, 1998 | Sums on a Cube |

December 19, 1997 | The Best Picture |

December 13, 1997 | A Square and a Straightedge |

December 3, 1997 | Peg Solitaire |

November 21, 1997 | Check(er)s and Balances |

November 14, 1997 | Dividing by 111 |

November 9, 1997 | The Blind Bartender |

October 31, 1997 | Tiling a Square |

October 24, 1997 | Books and Cannonballs |

October 17, 1997 | Two Fields |

October 10, 1997 | Rows of Checkers |

October 3, 1997 | Weekly Schedules |

September 26, 1997 | Reversed Products |

September 19, 1997 | Sums of Squares |

September 11, 1997 | Right Triangles |

September 4, 1997 | Acute Triangles |

August 28, 1997 | Five Floor Elevators |

August 17, 1997 | Quick Othello |

August 8, 1997 | Triominos |

August 1, 1997 | Crossing Ladders + |

July 25, 1997 | Olympic Ring Addition |

July 18, 1997 | Change for a Dollar |

July 10, 1997 | More Money |

July 3, 1997 | Points and Lines |

June 27, 1997 | Dominoes Again |

June 20, 1997 | Alternative Dice |

June 13, 1997 | Magic Cube |

June 9, 1997 | Nine Rounds |

May 30, 1997 | A Bumpy Plane |

May 20, 1997 | A Keg and a Jug |

May 17, 1997 | Non-Agressive Queens |

May 9, 1997 | Cards in a Circle |

May 1, 1997 | Five Weights |

April 24, 1997 | Alphabetical Numbers |

April 17, 1997 | Firing Squad |

April 10, 1997 | Crossing Chords |

April 1, 1997 | A Counter-Intuitive Trip, and a Product Square |

March 26, 1997 | Bob's House, and Productive Numbers Revisited |

March 18, 1997 | Two Lines and a Table |

March 11, 1997 | The Difference Pyramid |

March 4, 1997 | Two Dissections |

February 25, 1997 | Productive Numbers, and a Series |

February 18, 1997 | Nim |

February 6, 1997 | Quadrilaterals |

January 28, 1997 | Three Polygons |

January 18, 1997 | Cube Calendar |

January 11, 1997 | Three Fractions |

January 2, 1997 | The Obedient Ray |

December 26, 1996 | Coin Flip |

December 19, 1996 | Loops of Spaghetti |

December 10, 1996 | More Dominoes |

November 26, 1996 | Domino Magic Square |

November 19, 1996 | The Pentagram |

November 12, 1996 | A Geometric Progression |

November 5, 1996 | An Isosceles Triangle |

October 29, 1996 | A Set of Stamps |

October 15, 1996 | A Walking Puzzle |

October 8, 1996 | A Common Libel |

September 26, 1996 | A Tetrahedron |

September 19, 1996 | 10-Digit Numbers |

September 8, 1996 | The 10-Digit Digital Clock |

September 3, 1996 | The Josephus Problem |

August 27, 1996 | Magic Square |

August 20, 1996 | Two Rectangles |

August 13, 1996 | FORTY + TEN + TEN = SIXTY |

August 9, 1996 | Side of a Parallelogram |

August 6, 1996 | Running Total of a Die |

July 30, 1996 | P in a Square |