Q&A #19028

Teachers' Lounge Discussion: Everyday Mathematics slide rule

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From: Loyd

To: Teacher2Teacher Public Discussion
Date: 2010092411:33:55
Subject: Slide Rules

You can buy used slide rules on EBAY because every engineering student
used to own one.  I recently donated  3 or 4 slide rules to a church
yard sale.  So, they are still around.  But make sure you get an
instruction manual with it. I still have a 6 inch K&E. 

In college chemistry, our professor wanted us to use a circular slide
rule (that was before calculators).  They are the same idea as a
straight rule, but you don't run off at the ends.  The circular rule
was very good for solving ratio and proportion which are common in
chemistry and also physics.  

For example, 3 is to 4 as 6 is to x

For the circular, place the short hand on 3 and the long hand on 4. 
Without changing the spacing between the hands, put the short hand on
the 6.  The long hand will be over the 8. But even then, slide rules
are not too useful for simple arithmetic. You need to  know something
about logarithms, exponents and powers of 10 etc.   Most circular
rules were 4 inches in diameter, but I have seen them as large as 10

For the straight rule, you have a slip stick and a slide,  but the
idea is the same but takes a bit more thinking. And of course, you
still need to learn about logarithms and powers of ten, exponents etc,
to become proficient.  Slide rules are more for science and
engineering and not for arithmetic.  But they have been replaced by
calculators, spreadsheets, computers, etc. Most or all computers have
a scientific calculator as part of the basic software.   

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