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In mathematics, a multiplication table (sometimes, less formally, a times table) is a mathematical table used to define a multiplication operation for an algebraic system. The decimal multiplication table was traditionally taught as an essential part of elementary arithmetic around the world, as it lays the foundation for arithmetic operations with base-ten numbers. Many educators believe it is necessary to memorize the table up to 9 × 9.〔.〕 ==History== The oldest known multiplication tables were used by the Babylonians about 4000 years ago. They used base 60. The oldest known tables using base 10 are the decimal multiplication table on bamboo strips dating to about 305 BC, found in China.〔 The table is sometimes attributed to Pythagoras. It is also called the Table of Pythagoras in many languages (for example French, Italian and apparently Russian long ago), sometimes in English.〔for example in ( ''An Elementary Treatise on Arithmetic'' by John Farrar )〕 In 493 A.D., Victorius of Aquitaine wrote a 98-column multiplication table which gave (in Roman numerals) the product of every number from 2 to 50 times and the rows were "a list of numbers starting with one thousand, descending by hundreds to one hundred, then descending by tens to ten, then by ones to one, and then the fractions down to 1/144" (Maher & Makowski 2001, p. 383) In his 1820 book ''The Philosophy of Arithmetic'', mathematician John Leslie published a multiplication table up to 99 × 99, which allows numbers to be multiplied in pairs of digits at a time. Leslie also recommended that young pupils memorize the multiplication table up to 25 × 25. The illustration below shows a table up to 12 × 12, which is a common size to teach in schools. The traditional rote learning of multiplication was based on memorization of columns in the table, in a form like 1 × 10 = 10 2 × 10 = 20 3 × 10 = 30 4 × 10 = 40 5 × 10 = 50 6 × 10 = 60 7 × 10 = 70 8 × 10 = 80 9 × 10 = 90 This form of writing the multiplication table in columns with complete number sentences is still used in some countries instead of the modern grid above. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Multiplication table」の詳細全文を読む スポンサード リンク
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