Mathematicians and others -- can you still use a slide rule?

We had a couple at home when I was growing up, so I learned (to satisfy my curiosity) even though they had long since been replaced by calculators by the time I got to school.

There are devices that I commonly use in my work that use similar skills/principles, like vernier calipers and tapes that measure diameter (not circumference) when wrapped around a tree.

Yes. I have the beautiful Eugene Dietzgen one that my father gave me when I took Intro to Calculus during my senior year in high school. It sits on my desk with the manual (copyright 1928). I can’t imagine actually using it, but I enjoy owning it.

The print seems awfully small and, speaking of limits, the lines very close together (in the Trig. parts particularly).

My grandmother still uses a slide rule. I have no idea how it works. To be honest, I can’t do advanced math on the calculator either.

Disclaimer: I am not a mathematician.

The last time I used a slide rule was almost 40 years. I haven’t seen one since. How to use one might come back to me, so after a couple of trials and errors… probably, yes.

@mattbrowne: I bet that you’d need good reading glasses now.

I’m embarrassed to say this but… Yes, I can still use mine and do square and cube roots if you need any.

I learned how to use one in the eighth grade. (1978) I couldn’t do anything complicated on one then and I can’t now!

My husband is an engineer and loves to play with math. He still has a slide rule and plays with it on occasion.

I can, but I prefer my HP 48G.

I’ve got a K&E somewhere around, still have a couple of circular slide rules, they were in glove box for calculating gas mileage.

About every 5 years ago, I take it out and multiply a couple of numbers just to remember how. So yes, I supposed I do.

But it is not the first tool I turn to.

My daughters (both age 30+) say “what the heck is that?”

I could use one for multiplication, division and exponents in short order, and I think I’d get the hang of the trig functions again, too, with some practice.

But what slide rules have never been able to do is addition and subtraction. Since so many of my calculations involve these simple operations, I use the calculator function (or Excel) on my computer instead of the two perfectly serviceable and workable slide rules that I have from when I had to use them in the 1970s.

(Don’t ask me to remember how to explain logarithms, however. Adding logs instead of multiplying numbers? That seems weird.)

A little rusty, but I could pick it back up pretty quickly. I still have a circular (18 inch equivalent) and a 12 inch. Remember, length matters with a slide rule! lol I remember we carrying around slide rules like Jedi.

I’m no mathematician, but I did learn how to use a slide rule in high school. Now, I have no idea, whatsoever, even how to begin. I recently found my old side rule at my Mom’s house, while I was cleaning out a desk. I stared at the thing with absolutely no familiarity.

I recall that people could use those suckers for some fairly involved calculations.

I still have my dad’s good slide rule that my mom bought him and sent when he was in electrician’s school in the Navy, saw him through the first twenty years of a construction engineering career that lasted 40 years.

And I can still use it, although I am not as facile as I used to be in where the decimal point goes.

I can still multiply and divide on mine. I hang it on the belt of my Halloween ‘nerd’ costume, along with the pocket protector full of pens, black horn-rimmed glasses, and high-water trow.

Very few people know what it is.

It was terrible taking chemistry class problem tests with a slide rule. CALCULATORS were not allowed as they of course gave advantage. I can still multiply on a slide rule. BTW my mom had a job in the 50s teaching Computers. These were PEOPLE that the company used to do statistical analysis with pencils. At 84 she is on Windows 8 and I am supposed to figure it out and explain the quirks.

I used one occasionally in the days before calculators and I remember using tables of logarithms at school. It would probably come back to me if I ever had to use them.

I still have my dad’s, which I don’t think he ever used or could even work. Over the years I tried a few times to learn it but gave up.

I use google.

lol

Here’s something more modern for slide rule aficionados.

Once I get my cataract surgury later this week, I should again be able to use my sliderule. I know where it is, but the computer is still rather handy!

I created a Web page based on the slide rule. Did you know that with the proper scales you can use a slide rule to relativistically add velocities?

^^^ Clear and accessible data; congratulations. It is much more accessible (and with bigger font) than my 1929 manual, should I ever want to relearn that skill.

Thanks.

What gets lost in the manuals is the overview that the basic multiplication operation is just a variation of using two ordinary rulers for addition. The clever trick for slide rules is that the distances are proportional to the log of a number. When you add logs, you end up with the log of the product. It is really just that simple. log(x*Y) = log(x) + log(y)

What I tried to show was how you can get other useful results by varying the distance. For example, if we designate by x&y as the operation of getting the hypotenuse of a right triangle with sides x and y, then (x&y)^2 = x^2 + y^2. In this case we are adding squared distances instead of logs. By making distance proportional to the square of a number, you can get a slide rule to calculate the third side of a right triangle.

^^^ Um, Exedrin headache #32 here. I always had trouble intuitively grasping how logs worked and had to start from the beginning each time I used them. (Please don’t be nice and take the time to explain.)

At the risk of bringing on a headache, let me take my best and (I promise) only shot at an explanation. There are only two things you have to know. The first is by design and the second you will have to simply accept.

1. Numbers are marked on slide rule slides at a distance equal to log of number
2. log(x) + log(y) = log(xy)

Here is how these two things combine to allow you to multiply.
Let’s say you want to multiply 2 and 3 on the slide rule.

You move the start of the slide bar to line up with 2 on the bottom. It’s distance from the start is log(2) by the first rule.

Now you move the cursor to 3 along the slide, which, again by the first rule, is an additional distance of log(3)

The distance of the cursor relative to the start is log(2) + log(3), which by the second rule equals log(2*3) = log(6).

When you look on the bottom to see where the cursor falls, it will be the number at a distance of log(6), which by the using the first rule in reverse has to be 6.

^^^ Nicely and clearly put. It always helps, doesn’t it, to start with a simple example, and then move on to something more opaque?

And let us stick to base 10 only, please (please).

(Its is not synonymous with it’s)