… the slide rule?

Well, mine is in the bookcase behind me, Aviva! There’s my personal answer to your question that you posted in the **Padlet** devoted to this.

The educational year was my Grade 10. We were required to purchase a slide rule for mathematics class. We had two options:

- purchase a cheap plastic white tool or
- “if you’re serious about mathematics, you need to buy the upgraded yellow eye-saver metal one that comes with a finer hairline and a leather case.” (My mathematics teacher no-so-subtle advice)

As you can see in the picture above, using my chair as a background, I went with option #2 – A Pickett **N902-ES**

We were only allowed to take the slide rule to mathematics class. Apparently, it could be used as a weapon to avoid the boredom in other classes. (or so I heard), I remember the mathematics classrooms with a big teacher slide rule at the front of the class so that she/he could work along with us to solve problems with our slide rules.

We learned a great deal about mathematics from using that device including a new bit of language – “hair line”. It was true; when we would compare the two slide rule options, the yellow one did have a thinner hair line.

What difference does that make? It goes to the heart of using a slide rule. Unlike a calculator, it didn’t necessarily give you the exact answer. Instead, you learned the skill of estimation to get your answer. Unless you were working with integers, the hair line would fall on a scale and you needed to estimate just what the answer would be. I’ll tell you one thing; you sure learned about the beauty of numbers and decimal places. As I look at it while writing this post, there was a special marker for pi.

Flipping the slide rule over, in very tiny print, there were instructions about how to multiply, divide, find logarithms, find the sine of tangent of an angle, and the importance of the NUMBER OF ZEROS. You just knew that was important because, even back then, it was written in capital letters! There was also a grid of important fraction conversions – i.e. 45/64 = .703125 (Yes, I just did check it with my computer calculator)

It got me through that class and others in high school. Once I hit Statistics at university, it was incredibly clear that I needed to get with the digital age and purchased my first calculator – an **HP21. ** How sad is that that even the calculator is in the HP Calculator Museum.

I have no idea why I still have the slide rule; it doesn’t conveniently get stored anywhere and I can’t remember when I last used it.

Oh, fact check. Yes I do – re-read this blog post “**Two nerds walk into a Tim Horton’s**”

OK, I can’t remember the last time I used it since then…

Does that inspire you to do some thinking/reminiscing?

- have you ever used a slide rule?
- when did you buy your first calculator? Do you recall what features it had?
- if you’re a classroom teacher, how best do you teach number lines and estimating? Is it still an important skill?
- I know some manipulative kits use slide rules or close cousins to it. Have you ever used them?

Do you have an idea or thought that would be appropriate for my “Whatever happened to … ” series of blog posts like Aviva did? They can all, by the way, be revisited **here**.

Please visit this **Padlet** and add your idea. I’d love for it to be an inspiration for a post!

## Please share your thoughts here. I’d enjoy reading them.