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Genaille–Lucas rulers (also known as
Genaille's rods) is an arithmetic tool invented by Henri
Genaille, a French railway engineer, in 1891. The device
is a variant of Napier's bones. Example: 874 : 7
Start reading the result by the first number in the column of dividend's first digit, and in the row of the divisor (7), and follow the lines: 874 : 7 = 124 R 6
