| 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 |