Arithmetic

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

1. 3 glass puzzle [JavaScript]
   • 3 glasses puzzle, second, more general tool [JavaScript]
   • 3 Glasses Problem in Barycentric Coordinates
   • Three Jugs Problem [Java]
   • Two Pails Puzzle [Java]
2. A Line in a Square Grid [Java]
3. Abacus in Various Number Systems [Java]
4. About numbers
5. Absolute Value
6. Achieve the Equilibrium [Flash]
7. Algorithm for Computing LCM [Java]
8. The Aliquot Game [Java]
9. An Application of Mental Arithmetic to Highway Safety
10. An Arithmetic Magic Trick [Java]
11. An Inequality for Grade 8
12. An Interesting Number
13. Arithmetic magic matrix [Java]
14. Arithmetic Operations in Various Bases [Java]
15. Arithmetic Paradoxes
16. Bachet's Magic Trick [Java]
17. Barcode Encoding
18. Barcode Magic [Java]
19. Base Converter [JavaScript]
    • Binary System
    • Conversion of Fractions in Various Bases
    • Base (Binary, Decimal, etc.) Converter [Java]
20. Basic Rules of Counting
21. Binary Color Device [Java]
22. Binary Euclid's Algorithm
23. Breaking Chocolate Bars [Java]
24. Broken Calculator [Java]
25. Caterpillar [Flash]
26. Chameleons of Three Colors
27. Chinese Remainder Theorem
    • Chinese Remainder Theorem (Pigeonhole principle)
28. Collatz Conjecture [Java]
29. Compare Fractions: Interactive Practice [Java]
30. Computer As a Magician [Java]
31. Counting: The Beginning of Mathematics [Java]
    • Let Them Count
32. Counting Chips On a Circle [Java]
33. Counting Squares in a Square [Java]
34. Counting Triangles [Java]
35. Counting Triangles II [Java]
36. Covering A Chessboard With Domino
    • Dominoes on a Chessboard [Java]
37. Cryptarithms [JavaScript, Frames]
38. Distributive Law [Java]
39. Dividing Loot Fairly
40. Divisibility by 7
41. Divisibility by 9 and 11
42. Divisibility by 81
43. Divisibility Criteria
44. Divisibility by 7, 11, and 13
    • A Problem of Divisibility [Java]
45. EAN-13 Encoding [Java]
46. Egyptian Multiplication [Java]
47. Euclid's Algorithm
48. Euclid's Algorithm: An Interactive Illustration [Java]
49. Euclid's Game [Java]
50. Every composite number is the product of some factors and also the sum of the same numbers
51. Extension of Euclid's Algorithm
52. Factorials and division
53. Factoring with the Factor Tree [Java]
54. Falsity implies anything
55. Farey Series
56. Fast Arithmetic Tips
57. Formal Framework, an example
58. Formula for Primes
59. Four 3s
60. Four 4s
61. Four 5s
62. Four Pegs That Form a Square
    • Four Pegs That Form a Square [Java]
63. Four Weighings Suffice
64. Fraction Comparison [Java]
65. Fractions on a Binary Tree
66. Fractions on a Binary Tree II
67. Frieze Patterns [Java]
68. Fun with digits
69. Funny Arithmetic [JavaScript]
70. Gasoline Stations on a Circular Trek
71. GCD and LCM via Factoring
72. GCD(M, N) × LCM(M, N) = M × N [Java]
73. Geometric view of the Sieve of Eratosthenes [Java]
74. Gergonne Magic Trick [Java]
75. Heads and Tails [Java]
76. Hour glass timing
77. How to efficiently defend a castle
78. Identical Twins Puzzle
79. Identities in the Multiplication Table [Java]
80. Impossible Machine
81. Integer Iterations on a Circle [Java]
    • What Is Your Answer to That Question? [Java]
82. Integer Iterations on a Circle III [Java]
83. ISBN Encoding [Java]
84. Jumping Isn't Everything [Java]
85. Langford and Skolem Sequences [Java]
86. Latin Squares [Java]
    • Infinite Latin Squares
    • A Problem on an Infinite Checkerboard
87. Lattice Multiplication [Java]
88. Leibniz and Pascal Triangles [Java]
89. Less than, Equal to, Greater Than Symbols
90. Listing All the Composite Numbers [Java]
91. Long Multiplication [Java]
92. Long Runs of Composite Numbers
93. Loop or Halt [Java]
94. Magic in Square [Java]
95. Make An Identity [Java]
96. Make It All Zeros [Java]
97. Market Day
98. Math Card Trick
99. Math Telepathy [Java]
100. Mathematical Proof
101. Mediant Fractions
102. Minimax Principle [Java]
103. Modular Arithmetic [Java]
104. Napier Bones [Java]
105. Nine Squares [Java]
106. Number Guessing Game [Java]
107. Number sequences and Pigeonhole [Java]
108. Number System With Base 36
109. One Dimensional Ants
110. Operations on Fractions [Java]
111. Order. Well-ordered sets.
112. Ordinal Numbers
113. Outline Mathematics
     Billy is twice as old as Sally [Java]
     Coin Counting Word Problem [Java]
     Crab's Weight [Java]
     "Math trick" with two dice [Java]
     Primes as differences of squares [Java]
     Problem #24 from the Rhind Papyrus [Java]
     Robbery #1 [Java]
     Robbery #2 [Java]
     Robbery #3 [Java]
     Robbery #4 [Java]
     Smallest multiple of 9 with no odd digits [Java]
     The Lucky Find [Java]
     Three digit twister [Java]
     Who Has Beard? [Java]
114. Parity counting [Java]
115. Party Acquaintances [Java]
116. Peasant Multiplication [Java]
117. Pennies in Boxes [Java]
118. Permutations
     • Permutations as a Product of Transpositions
119. Pigeonhole Principle
     • Pigeonhole Principle and Extensions
120. Place Value [Java]
     • Letter Count in a Sentence [Java]
121. Probability of Divisibility
122. Product of Simple Fractions [Java]
123. Proizvolov's Identity [Java]
124. Proofs Without Words [Java]
125. Yet Another Puzzle with Hats
126. Represent 4 with four digits
127. Represent 6 with three digits
128. Review of Arithmetic for Parents: A Book for Grownups about Children's Mathematics by R. Aharoni
129. Rhind Papyrus
130. Right Replacement [Java]
131. Russell's Paradox
132. Scrub Tile Puzzle [Java]
133. Self-descriptive Strings [Java]
134. Self-reference
135. Seven Terms Periodic Sequence
136. Ship-Dock Theorem
     • Ship-Dock Theorem,a formalization
137. Sieve of Eratosthenes [Java]
138. Sieve of Squares [Java]
139. Simple Cellular Automaton [Java]
140. Six Balls, Two Weighings
141. Slider Puzzles [Java]
142. Solitaire in Two Colors [Java]
143. Soriteses
144. Soroban in Various Number Systems
145. Splitting piles
146. Squares, Circles, and Triangles [Java]
147. Steinhaus' Problem [Java]
148. Stern-Brocot Tree
149. Straight Tromino on a Chessboard [Java]
150. Suan Pan in Various Number Systems [Java]
151. Subtraction Game [Java]
152. Sums and Products [Java]
153. Sums of powers of digits [Java]
154. Superposition Principle
155. The ass and the mule [Java]
156. Three 3s
157. Three 4s
158. Three 5s
159. Tool for Constructing Orthogonal Latin Squares [Java]
160. Two Colors in Two Rows [Java]
     • Two Colors in Two Rows II [Java]
161. Two Numbers Guessing Game [Java]
162. Uncountability of the Reals - via a Game
163. Universal Product Code [Java]
164. Unproperty of the Powers of 2
165. Weighing 12 coins
     • Oddball Problem
     • Odd Coin Problems
166. What, how, and the Web [Java]
167. What Is Fraction?
168. Why 1/3 + 1/4 = 7/12?
169. With One 4
170. Wolf and Rabbit [Flash]
171. Word Problems [Java]
172. Zeros and Nines [Java]

Copyright © 1996-2010 Alexander Bogomolny