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2. Napier's bones - Wikipedia

   en.wikipedia.org/wiki/Napier's_bones

   Napier gave details of a scheme for arranging the tables so that no rod has two copies of the same table, enabling every possible four-digit number to be represented by 4 of the 10 rods. A set of 20 rods, consisting of two identical copies of Napier's 10 rods, allows calculation with numbers of up to eight digits, and a set of 30 rods can be ...

3. Genaille–Lucas rulers - Wikipedia

   en.wikipedia.org/wiki/Genaille–Lucas_rulers

   Genaille–Lucas rulers (also known as Genaille's rods) are an arithmetic tool invented by Henri Genaille, a French railway engineer, in 1891. The device is a variant of Napier's bones . By representing the carry graphically, the user can read off the results of simple multiplication problems directly, with no intermediate mental calculations .

4. Rabdology - Wikipedia

   en.wikipedia.org/wiki/Rabdology

   The first device, which by then was already popularly used and known as Napier's bones, was a set of rods inscribed with the multiplication table. Napier coined the word rabdology (from Greek ῥάβδος [rhabdos], rod and λόγoς [logos] calculation or reckoning) to describe this technique. The rods were used to multiply, divide and even ...

5. Promptuary - Wikipedia

   en.wikipedia.org/wiki/Promptuary

   The promptuary contains a lot more pieces than a set of Napier's Bones. A set of Napier's Bones with 20 rods is capable of multiplying numbers of up to 8 digits. An equivalent promptuary needs 160 strips. In the examples and illustrations below, N is set to 5 - that is, the illustrated promptuary can multiply numbers of up to 5 digits.

6. Rod calculus - Wikipedia

   en.wikipedia.org/wiki/Rod_calculus

   Start calculating from the highest place of the multiplicand (in the example, calculate 30×76, and then 8×76). Using the multiplication table 3 times 7 is 21. Place 21 in rods in the middle, with 1 aligned with the tens place of the multiplier (on top of 7). Then, 3 times 6 equals 18, place 18 as it is shown in the image.

7. Multiplication table - Wikipedia

   en.wikipedia.org/wiki/Multiplication_table

   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 ...