Need a slide rule?

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JPG
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Post by JPG »

shaun wrote:Now that's funny! (But you've prolly gotta be older than a "Generation X'er" to appreciate it.)
Wonder how long before we need to 'explain' it!:D
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Goldie(Bought New SN 377425)/4" jointer/6" beltsander/12" planer/stripsander/bandsaw/powerstation /Scroll saw/Jig saw /Craftsman 10" ras/Craftsman 6" thicknessplaner/ Dayton10"tablesaw(restoredfromneighborstrashpile)/ Mark VII restoration in 'progress'/ 10E[/size](SN E3779) restoration in progress, a 510 on the back burner and a growing pile of items to be eventually returned to useful life. - aka Red Grange
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fredsheldon
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Post by fredsheldon »

JPG40504 wrote:Wonder how long before we need to 'explain' it!:D
How about 2 minutes???:D
Fred Sheldon
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JPG
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Post by JPG »

fredsheldon wrote:How about 2 minutes???:D

Slide rules are based upon logarithms.

Every number value has a unique logarithm. IIRC the 'C' and 'D' scales are base 10 logarithms.

When the logarithms of two numbers are added, the sum equals the logarithm of the product of the two numbers.

The index of the C scale is placed upon one of the numbers, the slider is placed upon the second number of the D scale and the 'result' is then read from the DS scale.

In my previous 2 x 3 = 6 example(post #5),the C index is positioned on '2' of the D scale. The slider is positioned on '3' of the C scale. The result is read as '6' on the D scale.



So adders (a slide rule is an adding device) need logs (logarithmic scales) to multiply. No neither this 'explanation' nor the scales is 'fishy'!:D


FWIW, the c/d scales may be reversed as can the two numbers and the direction of parts movement as well. Tis all 'commutative'!:cool:
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╟JPG ╢
╚═══╝

Goldie(Bought New SN 377425)/4" jointer/6" beltsander/12" planer/stripsander/bandsaw/powerstation /Scroll saw/Jig saw /Craftsman 10" ras/Craftsman 6" thicknessplaner/ Dayton10"tablesaw(restoredfromneighborstrashpile)/ Mark VII restoration in 'progress'/ 10E[/size](SN E3779) restoration in progress, a 510 on the back burner and a growing pile of items to be eventually returned to useful life. - aka Red Grange
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