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Knitted Napier's Bones



Because they are awesome, Pat Ashforth, Steve Plummer and Ben Ashforth illustrate math through their crafting projects. Pictured above is their knitted version of Napier's Bones, a calculation device invented by Scottish mathematician John Napier (1550-1617). George Hart explains how they work:

The image below shows how to arrange the bones if you wanted to multiply by 76495. For example, the bottom row, labeled 9 at left, allows you to read off 9 x 76495. The rightmost digit of the answer is the 5 seen in the triangle at right. Then read off the remaining digits by adding the two numbers in each parallelogram, carrying as necessary, e.g., 1+4 gives 5 as the next digit and 6+8=14 gives 4 as the following digit, with a carry of 1 into the digit after that. The result can be quickly read off as 688455.


Crafters' Website -via Make

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They put the wrong image up for the explanation that they are giving. Hit Make and it will take you too the proper image and description.
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Check out Twaggies' very funny clip:

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