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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 x 7
Start reading the result by the first number in the right hand column (8), and follow the triangles: To multiply a multidigit number by a multidigit number, calculate partial products and add: Example: 874 x 73 = 874 x 70 + 874
x 3
874 x 7 = 6118add : 61180 +2622 _________ result: 63802 