Arithmetic articles, problems, and puzzles

What Is Arithmetic?
What Is Algebra?
Mental Calculations
Algebra: Articles and Problems

  1. 100 Grasshoppers on a Triangular Board
  2. 1089 and a Property of 3-digit Numbers [Java]
  3. 12 Coins in Verse
  4. 24 with One Digit
  5. 3 glass puzzle [JavaScript]
  6. A Farewell Problem for the Year 2017
  7. A Welcome Problem for the Year 2018
  8. A Line in a Square Grid [Java]
  9. A Missing Digit
  10. A Number Theoretic Problem With the Floor Function [JavaScript]
  11. A Problem from the 1967 IMO Shortlist
  12. A Problem That Fermat Might Have Liked
  13. A Property of Unimodal Integers as a Whole [JavaScript]
  14. A Quadratic Equation in Three Variables
  15. A Remote Decimal Digit
  16. A Short Equation in Reciprocals
  17. Abacus in Various Number Systems [Java]
  18. About numbers
  19. Absolute Value
  20. Achieve the Equilibrium [Flash]
  21. Adding a Long List of Numbers
  22. Addition and Subtraction of Integers
  23. Algorithm for Computing LCM [Java]
  24. Aliquot Game [Java]
  25. An Application of Mental Arithmetic to Highway Safety
  26. An Arithmetic Magic Trick [Java]
  27. An Equation Involving the Total Number of Digits
  28. An Inequality for Grade 8
  29. An Interesting Number
  30. An Age Conundrum with Men of the Cloth
  31. An Equation in Integers and Rational Numbers [JavaScript]
  32. An Olympiad Problem With the Floor Function [JavaSCript]
  33. Arithmetic magic matrix [Java]
  34. Arithmetic Operations in Various Bases [Java]
  35. Arithmetic Paradoxes
  36. Bachet's Magic Trick [Java]
  37. Barcode Encoding
  38. Barcode Magic [Java]
  39. Base Converter [JavaScript]
  40. Basic Rules of Counting
  41. Billiard Handicap
  42. Binary Color Device [Java]
  43. Binary Euclid's Algorithm
  44. Breaking Chocolate Bars [Java]
  45. Broken Calculator [Java]
  46. Caterpillar [Flash]
  47. Chameleons of Three Colors
  48. Chinese Remainder Theorem
  49. Collatz Conjecture [Java]
  50. Common Multiples and the Least Common Multiple [Java]
  51. Compare Fractions: Interactive Practice [Java]
  52. Computer As a Magician [Java]
  53. Counting and Equivalent Fractions
  54. Counting: The Beginning of Mathematics [Java]
  55. Counting Chips On a Circle [Java]
  56. Counting Squares in a Square [Java]
  57. Counting Triangles [Java]
  58. Counting Triangles II [Java]
  59. Covering A Chessboard With Domino
  60. Cryptarithms [JavaScript, Frames]
  61. Curious Identities Involving Integer Squares
  62. Distributive Law [Java]
  63. Dividing Loot Fairly
  64. Divisibility by 7
  65. Divisibility by 9 and 11
  66. Divisibility by 81
  67. Divisibility Criteria
  68. Divisibility by 7, 11, and 13
  69. Doubling Investment for a Fee And Getting Zero [JavaScript]
  70. EAN-13 Encoding [Java]
  71. Egyptian Multiplication [Java]
  72. Elegance in Integers by Dorin Marghidanu
  73. Euclid's Algorithm
  74. Euclid's Algorithm: An Interactive Illustration [Java]
  75. Euclid's Game [Java]
  76. Euclid's Game on a Square Grid [Java]
  77. Every composite number is the product of some factors and also the sum of the same numbers
  78. Extension of Euclid's Algorithm
  79. Factorial Divisibility
  80. Factorials and division
  81. Factoring with the Factor Tree [Java]
  82. Factors And Multiples
  83. Falsity implies anything
  84. Farey Series
  85. Fast Arithmetic Tips
  86. Fibonacci Numbers in Equilateral Triangle
  87. Finger Counting
  88. Formal Framework, an example
  89. Formula for Primes
  90. Four 3s
  91. Four 4s
  92. Four 5s
  93. Four Pegs That Form a Square
  94. Four Weighings Suffice
  95. Fraction Comparison [Java]
  96. Fraction Comparison Sped up [Java]
  97. Fractions on a Binary Tree
  98. Fractions on a Binary Tree II
  99. Frieze Patterns [Java]
  100. Fun with digits
  101. Funny Arithmetic [JavaScript]
  102. Gasoline Stations on a Circular Trek
  103. GCD and LCM via Factor Tree [Java]
  104. GCD and LCM by Plain Factorization [Java]
  105. GCD(M, N) × LCM(M, N) = M × N [Java]
  106. Geometric view of the Sieve of Eratosthenes [Java]
  107. Gergonne Magic Trick [Java]
  108. Grandfather's Bill [Javascript]
  109. Hardy's Example of Non-Serious Theorems
  110. Heads and Tails [Java]
  111. Hour glass timing
  112. How to efficiently defend a castle
  113. Identical Twins Puzzle
  114. Identities in the Multiplication Table [Java]
  115. Illustrated Sum of Cubes - All in a Plane
  116. Impossible Machine
  117. Infinitely many proofs that there are infinitely many primes
  118. Infinitude of Primes Via Powers of 2
  119. Integer Iterations on a Circle [Java]
  120. Integer Iterations on a Circle III [Java]
  121. ISBN Encoding [Java]
  122. Jumping Isn't Everything [Java]
  123. Langford and Skolem Sequences [Java]
  124. Latin Squares [Java]
  125. Lattice Multiplication [Java]
  126. Leibniz and Pascal Triangles [Java]
  127. Less than, Equal to, Greater Than Symbols
  128. Listing All the Composite Numbers [Java]
  129. Long Multiplication [Java]
  130. Long Runs of Composite Numbers
  131. Looking for the Prime Decomposition
  132. Loop or Halt [Java]
  133. Magic in Square [Java]
  134. Make An Identity [Java]
  135. Make It All Zeros [Java]
  136. Many Jugs to One I
  137. Many Jugs to One II
  138. Market Day
  139. Math Card Trick
  140. Math Telepathy [Java]
  141. Mathematical Proof
  142. Mathematicians and Musicians [JavaScript]
  143. Mediant Fractions
  144. Minimax Principle [Java]
  145. Modular Arithmetic [Java]
  146. Moving Chips in Pairs Down a Checkerboard [Java]
  147. Napier Bones [Java]
  148. Negative Coconuts
  149. Nine Squares [Java]
  150. Number Guessing Game [Java]
  151. Number of Factors of an Integer
  152. Number sequences and Pigeonhole [Java]
  153. Number System With Base 36
  154. Numbers That Divide the Others' Sum
  155. Odd Scoring [Java]
  156. On Gauss' Shoulders
  157. One Dimensional Ants
  158. Operations on Fractions [Java]
  159. Order. Well-ordered sets.
  160. Ordinal Numbers
  161. Outline Mathematics
  162. Parity counting [Java]
  163. Party Acquaintances [Java]
  164. Peasant Multiplication [Java]
  165. Pennies in Boxes [Java]
  166. Permutations
  167. Pigeonhole Principle
  168. Place Value [Java]
  169. Powers of 6 and 7771
  170. Probability of Divisibility
  171. Problem 4132 from Crux Mathematicorum
  172. Product of Simple Fractions [Java]
  173. Proizvolov's Identity [Java]
  174. Proofs Without Words [Java]
  175. Properties of GCD and LCM
  176. Psychology of 0.99999...
  177. Question That Changes with Time
  178. Represent 4 with four digits
  179. Representation of 3 with Three Equal Digits
  180. Represent 6 with three digits
  181. Review of Arithmetic for Parents: A Book for Grownups about Children's Mathematics by R. Aharoni
  182. Rhind Papyrus
  183. Right Replacement [Java]
  184. The Rule of Change of Addends [Java]
  185. Russell's Paradox
  186. Scrub Tile Puzzle [Java]
  187. Self-descriptive Strings [Java]
  188. Self-reference
  189. Seven Terms Periodic Sequence
  190. Ship-Dock Theorem
  191. Sieve of Eratosthenes [Java]
  192. Sieve of Squares [Java]
  193. Simple Cellular Automaton [Java]
  194. Six Balls, Two Weighings
  195. Six Misnamed Coins, Two Weighings
  196. Slider Puzzles [Java]
  197. Solitaire in Two Colors [Java]
  198. Soriteses
  199. Soroban in Various Number Systems
  200. Splitting piles
  201. Squares, Circles, and Triangles [Java]
  202. Steinhaus' Problem [Java]
  203. Stern-Brocot Tree
  204. Straight Tromino on a Chessboard [Java]
  205. Suan Pan in Various Number Systems [Java]
  206. Subtraction Game [Java]
  207. Subtraction in a Rectangular Array [Java]
  208. Sums and Products [Java]
  209. Sums of powers of digits [Java]
  210. Superposition Principle
  211. Tables for Multiplication
  212. The ass and the mule [Java]
  213. Three 3s
  214. Three 4s
  215. Three 5s
  216. Tony Foster's Integer Powers in Pascal's Triangle
  217. Tool for Constructing Orthogonal Latin Squares [Java]
  218. Treasure Hunt in a Square Grid
  219. Treasure Hunt from Outside the Grid
  220. Two Colors in Two Rows [Java]
  221. Two Numbers Guessing Game [Java]
  222. Uncountability of the Reals - via a Game
  223. Uniqueness of Number 5
  224. Universal Product Code [Java]
  225. Unproperty of the Powers of 2
  226. Using Math Rules: An Example
  227. Weighing 12 coins
  228. What, how, and the Web [Java]
  229. What Is Fraction?
  230. When Two Wrongs Make One Right
  231. Why 1/3 + 1/4 = 7/12?
  232. With One 4
  233. With One Weighing
  234. Wolf and Rabbit [Flash]
  235. Word Problems [Java]
  236. Yet Another Puzzle with Hats
  237. Zeros and Nines [Java]

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