Multiplication table
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 baseten numbers. Many educators believe it is necessary to memorize the table up to 9 × 9.^{[1]}
Contents
History
The oldest known multiplication tables were used by the Babylonians about 4000 years ago. They used base 60.^{[2]} The oldest known tables using base 10 are the decimal multiplication table on bamboo strips dating to about 305 BC, found in China.^{[2]}
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.^{[4]}
In 493 A.D., Victorius of Aquitaine wrote a 98column 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,^{[5]} 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.
×  1  2  3  4  5  6  7  8  9  10  11  12 

1  1  2  3  4  5  6  7  8  9  10  11  12 
2  2  4  6  8  10  12  14  16  18  20  22  24 
3  3  6  9  12  15  18  21  24  27  30  33  36 
4  4  8  12  16  20  24  28  32  36  40  44  48 
5  5  10  15  20  25  30  35  40  45  50  55  60 
6  6  12  18  24  30  36  42  48  54  60  66  72 
7  7  14  21  28  35  42  49  56  63  70  77  84 
8  8  16  24  32  40  48  56  64  72  80  88  96 
9  9  18  27  36  45  54  63  72  81  90  99  108 
10  10  20  30  40  50  60  70  80  90  100  110  120 
11  11  22  33  44  55  66  77  88  99  110  121  132 
12  12  24  36  48  60  72  84  96  108  120  132  144 
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.
Patterns in the tables
There is a pattern in the multiplication table that can help people to memorize the table more easily. It uses the figures below:
→  →  
↑  1  2  3  ↓  ↑  2  4  ↓  

4  5  6  
7  8  9  6  8  
←  ←  
0  5  0  
Figure 1: Odd  Figure 2: Even 
Figure 1 is used for multiples of 1, 3, 7, and 9. Figure 2 is used for the multiples of 2, 4, 6, and 8. These patterns can be used to memorize the multiples of any number from 0 to 10, except 5. As you would start on the number you are multiplying, when you multiply by 0, you stay on 0 (0 is external and so the arrows have no effect on 0, otherwise 0 is used as a link to create a perpetual cycle). The pattern also works with multiples of 10, by starting at 1 and simply adding 0, giving you 10, then just apply every number in the pattern to the "tens" unit as you would normally do as usual to the "ones" unit.
For example, to recall all the multiples of 7:
 Look at the 7 in the first picture and follow the arrow.
 The next number in the direction of the arrow is 4. So think of the next number after 7 that ends with 4, which is 14.
 The next number in the direction of the arrow is 1. So think of the next number after 14 that ends with 1, which is 21.
 After coming to the top of this column, start with the bottom of the next column, and travel in the same direction. The number is 8. So think of the next number after 21 that ends with 8, which is 28.
 Proceed in the same way until the last number, 3, corresponding to 63.
 Next, use the 0 at the bottom. It corresponds to 70.
 Then, start again with the 7. This time it will correspond to 77.
 Continue like this.
In abstract algebra
Tables can also define binary operations on groups, fields, rings, and other algebraic systems. In such contexts they can be called Cayley tables. Here are the addition and multiplication tables for the finite field Z_{5}.
For every natural number n, there are also addition and multiplication tables for the ring Z_{n}.


For other examples, see group, and octonion.
Chinese multiplication table
The Chinese multiplication table consists of eightyone sentences with five Chinese characters per sentence, making it is easy for children to learn by heart. A shorter version of the table consists of only fortyfive sentences, as terms such as "nine eights beget seventytwo" are identical to "eight nines beget seventytwo" so there is no need to learn them twice.
Warring States decimal multiplication bamboo slips
A bundle of 21 bamboo slips dated 305 B.C. in the Warring States period in the Tsinghua Bamboo Slips (清华简) collection is the world's earliest known example of a decimal multiplication table.^{[6]}
Standardsbased mathematics reform in the USA
In 1989, the National Council of Teachers of Mathematics (NCTM) developed new standards which were based on the belief that all students should learn higherorder thinking skills, and which recommended reduced emphasis on the teaching of traditional methods that relied on rote memorization, such as multiplication tables. Widely adopted texts such as Investigations in Numbers, Data, and Space (widely known as TERC after its producer, Technical Education Research Centers) omitted aids such as multiplication tables in early editions. NCTM made it clear in their 2006 Focal Points that basic mathematics facts must be learned, though there is no consensus on whether rote memorization is the best method.
See also
 Chinese multiplication table
 Division table
 Vedic square
 IBM 1620, an early computer that used tables stored in memory to perform addition and multiplication.
References
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 ↑ Wikisource:Page:Popular Science Monthly Volume 26.djvu/467
 ↑ for example in An Elementary Treatise on Arithmetic by John Farrar
 ↑ Leslie, John (1820). The Philosophy of Arithmetic; Exhibiting a Progressive View of the Theory and Practice of Calculation, with Tables for the Multiplication of Numbers as Far as One Thousand. Edinburgh: Abernethy & Walker.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
 ↑ Nature article The 2,300yearold matrix is the world's oldest decimal multiplication table