Archive (by date): *=Unsolved. %=Partially solved. +=Recently solved.
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 %

Ken's Puzzle of the Week: The Twelvth Year (8/1/07-7/31/08)
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

Ken's Puzzle of the Week: The Eleventh Year (8/1/06-7/31/07)
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

Ken's Puzzle of the Week: The Tenth Year (8/1/05-7/31/06)
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

Ken's Puzzle of the Week: The Ninth Year (8/16/04-7/27/05)
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

Ken's Puzzle of the Week: The Eighth Year (8/5/03-7/23/04)
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

Ken's Puzzle of the Week: The Seventh Year (7/25/02-7/28/03)
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

Ken's Puzzle of the Week: The Sixth Year (7/25/01-7/25/02)
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

Ken's Puzzle of the Week: The Fifth Year (7/28/00-7/25/01)
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

Ken's Puzzle of the Week: The Fourth Year (7/30/99-7/13/00)
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

Ken's Puzzle of the Week: The Third Year (8/3/98-7/27/99)
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

Ken's Puzzle of the Week: The Second Year (7/25/97-7/27/98)
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

Ken's Puzzle of the Week: The First Year (7/31/96-7/18/97)
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