Using your Head is Permitted

Welcome to the "Using your Head is Permitted" monthly math riddle page.

Links to past riddles and solutions are from this page. If you know any good riddles that you think might fit in, you're welcome to send them to the puzzlemaster at riddlesbrand.scso.com. The puzzlemaster is Michael Brand.

128. October 2017 Riddle Solution Coda
127. September 2017 Riddle Solution Real Sorting
126. August 2017 Riddle Solution Open Day Riddle
125. July 2017 Riddle Solution Two Classics
124. June 2017 Riddle Solution Real Random Walk
123. May 2017 Riddle Solution More One-to-one Functions
122. April 2017 Riddle Solution Soko-2048-ban
121. March 2017 Riddle Solution Ten Years of UyHiP
120. February 2017 Riddle Solution Sublinear Primes
119. January 2017 Riddle Solution Linear Primes
118. December 2016 Riddle Solution Return to Prepostria
117. November 2016 Riddle Solution Leibniz 300
116. October 2016 Riddle Solution Concave Quadrilaterals
115. September 2016 Riddle Solution Random Errors
114. August 2016 Riddle Solution Mutual Acquaintances
113. July 2016 Riddle Solution Tower of Hats
112. June 2016 Riddle Solution Three Stone Paths
111. May 2016 Riddle Solution Means
110. April 2016 Riddle Solution Which Number?
109. March 2016 Riddle Solution MFCIS Margin
108. February 2016 Riddle Solution Planes on a Hypercube
107. January 2016 Riddle Solution Latin
106. December 2015 Riddle Solution Common Subgraphs
105. November 2015 Riddle Solution Unbiased Estimation
104. October 2015 Riddle Solution Universal Probabilities
103. September 2015 Riddle Solution Coins on a Board
102. August 2015 Riddle Solution 3xn+1
101. July 2015 Riddle Solution Centenary
100. June 2015 Riddle Solution Odds and Evens
99. May 2015 Riddle Solution Expanding Sets
98. April 2015 Riddle Solution Even More Quadrilateral Inequalities
97. March 2015 Riddle Solution More Quadrilateral Inequalities
96. February 2015 Riddle Solution Quadrilateral Inequality
95. January 2015 Riddle Solution Surjection/Injection
94. December 2014 Riddle Solution Casinos
93. November 2014 Riddle Solution One Coin
92. October 2014 Riddle Solution Two Coins
91. September 2014 Riddle Solution Even More Jigsaw Puzzles
90. August 2014 Riddle Solution Balancing Rounded Irrationals
89. July 2014 Riddle Solution More Jigsaw Puzzles
88. June 2014 Riddle Solution The Missing Piece
87. May 2014 Riddle Solution Fun with Random Bits
86. April 2014 Riddle Solution 2048
85. March 2014 Riddle Solution Squares and Rectangles
84. February 2014 Riddle Solution On the Shoulders of Giants
83. January 2014 Riddle Solution Table-turning Genie
82. December 2013 Riddle Solution Christmas at MegaCorp
81. November 2013 Riddle Solution Parenthesis Values
80. October 2013 Riddle Solution King Tours
79. September 2013 Riddle Solution Rook Tours
78. August 2013 Riddle Solution Fun with L2
77. July 2013 Riddle Solution PSP
76. June 2013 Riddle Solution Horner's Dilemma
75. May 2013 Riddle Solution Coin Verification
74. April 2013 Riddle Solution k-resistance
73. March 2013 Riddle Solution A185028
72. February 2013 Riddle Solution More Takeaways
71. January 2013 Riddle Solution Take Away
70. December 2012 Riddle Solution A Problem with Neighbors
69. November 2012 Riddle Solution Fun with Normal Distributions
68. October 2012 Riddle Solution Rectangling Another Rectangle
67. September 2012 Riddle Solution Hydra Games
66. August 2012 Riddle Solution Euler Numbers
65. July 2012 Riddle Solution Stepping Contest
64. June 2012 Riddle Solution Lucky Numbers
63. May 2012 Riddle Solution Two Polygons
62. April 2012 Riddle Solution Natural Partitions
61. March 2012 Riddle Solution Rectangling the Rectangle
60. February 2012 Riddle Solution Space-efficient Exponentiation
59. January 2012 Riddle Solution From A to B
58. December 2011 Riddle Solution Post-office Tetrahedra
57. November 2011 Riddle Solution Post-office Volumes
56. October 2011 Riddle Solution Post-office Dilemma
55. September 2011 Riddle Solution Gladiators
54. August 2011 Riddle Solution Equinox Counting
53. July 2011 Riddle Solution Bananas
52. June 2011 Riddle Solution Improved FFT
51. May 2011 Riddle Solution Fun with Trigonometry
50. April 2011 Riddle Solution Cyclone Frogs
49. March 2011 Riddle Solution Lights-Out
48. February 2011 Riddle Solution Tea or Coffee
47. January 2011 Riddle Solution Prepostria
46. December 2010 Riddle Solution 2-bend Graph Embeddings
45. November 2010 Riddle Solution DNFs and Symmetric Functions
44. October 2010 Riddle Solution Abraham and Benjamin
43. September 2010 Riddle Solution Gloved Prisoners
42. August 2010 Riddle Solution Tetrahedron Crossing
41. July 2010 Riddle Solution A Tribute to Gardner
40. June 2010 Riddle Solution Cyclic Permutations
39. May 2010 Riddle Solution Segment-preserving Mappings
38. April 2010 Riddle Solution Self Assembled Numbers
37. March 2010 Riddle Solution Taylor Series
36. February 2010 Riddle Solution Laura Sort
35. January 2010 Riddle Solution Encyclopedia Sort
34. December 2009 Riddle Solution Dividing the Naturals
33. November 2009 Riddle Solution Polynomial Solutions
32. October 2009 Riddle Solution Local Minima
31. September 2009 Riddle Solution Pythagorean Triplets
30. August 2009 Riddle Solution Boolean Functions
29. July 2009 Riddle Solution Steiner Systems with k=3
28. June 2009 Riddle Solution Counting Solutions to x2+y2
27. May 2009 Riddle Solution Perfect Numbers
26. April 2009 Riddle Solution Counting Triangles
25. March 2009 Riddle Solution Fun with Uniform Distributions
24. February 2009 Riddle Solution O(1) Factorial
23. January 2009 Riddle Solution O(1) Sorting
22. December 2008 Riddle Solution O(n) Sorting
21. November 2008 Riddle Solution Combinations of 1s
20. October 2008 Riddle Solution
19. September 2008 Riddle Solution Permutation Reversal
18. August 2008 Riddle Solution Trisecting the Square
17. July 2008 Riddle Solution Sudoku
16. June 2008 Riddle Solution Knights of the Round Table
15. May 2008 Riddle Solution Permutation Partial Sums
14. April 2008 Riddle Solution Partial Harmonic Series
13. March 2008 Riddle Solution Lexicographic Sorting
12. February 2008 Riddle Solution Board Game Strategies
11. January 2008 Riddle Solution QCPL
10. December 2007 Riddle Solution One-to-one Functions
9. November 2007 Riddle Solution License Plate Numbers
8. October 2007 Riddle Solution Jigsaw Puzzles
7. September 2007 Riddle Solution Clique Partitioning
6. August 2007 Riddle Solution Three Points through every Line
5. July 2007 Riddle Solution Digit Anagrams
4. June 2007 Riddle Solution Mesh Animals
3. May 2007 Riddle Solution Chico and Dico
2. April 2007 Riddle Solution 3025
1. March 2007 Riddle Solution Primitive Polynomials

Enjoy!