Pi in a pinch: Most of us know that 22/7 is the conventional rational approximation to Pi, but it is only good for two decimal places. If you need more precision and do not have a...

clemente21

Most of us know that 22/7 is the conventional rational approximation to Pi, but it is only good for two decimal places.

If you need more precision and do not have a calculator with the constant, using 355/113 will take you to about six decimal places.

Longshadow Loc: Audubon, PA, United States

clemente21 wrote:

Most of us know that 22/7 is the conventional rational approximation to Pi, but it is only good for two decimal places.

If you need more precision and do not have a calculator with the constant, using 355/113 will take you to about six decimal places.

In electronics class in high school we used it a LOT: 3.1415926 has been in my head for YEARS!

And we did it on a slip-stick.

twowindsbear

Longshadow wrote:

In electronics class in high school we used it a LOT: 3.1415926 has been in my head for YEARS!

And we did it on a slip-stick.

How do you get all that precision on a slip-stick?

and yes, I know what a slip-stick is & how to use the one I have

Longshadow Loc: Audubon, PA, United States

twowindsbear wrote:

How do you get all that precision on a slip-stick?

and yes, I know what a slip-stick is & how to use the one I have

We had calibrated eyelashes, at least that's what the teacher said.

BBurns Loc: South Bay, California

Longshadow wrote:

We had calibrated eyelashes, at least that's what the teacher said.

I had a 18" SUN log/log bamboo slip stick.
It was accurate to 4 places.

pendennis

BBurns wrote:

I had a 18" SUN log/log bamboo slip stick.
It was accurate to 4 places.

and "guess to six".

My quantitative business analysis professor taught us that.

I still have my Dietzgen, K&E, and Post slide rules; all bamboo.

Longshadow Loc: Audubon, PA, United States

pendennis wrote:

and "guess to six".

My quantitative business analysis professor taught us that.

I still have my Dietzgen, K&E, and Post slide rules; all bamboo.

Some of us could guess better.

BBurns Loc: South Bay, California

pendennis wrote:

and "guess to six"....still have my Dietzgen, K&E, and Post slide rules; all bamboo.

I still have 3 or 4. My K&E is aluminum. Always kept one on my work desk.
New engineers fresh out of school would always ask what they were?
My answer was, 'Analog calculators, no batteries needed.'
I would freak out the really curious by handing them my Series 1 Curta 'pepper mill'.

IDguy Loc: Idaho

Longshadow wrote:

In electronics class in high school we used it a LOT: 3.1415926 has been in my head for YEARS!

And we did it on a slip-stick.

I remember it too but you only needed 3.14 on a slide rule.

IDguy Loc: Idaho

BBurns wrote:

I still have 3 or 4. My K&E is aluminum. Always kept one on my work desk.
New engineers fresh out of school would always ask what they were?
My answer was, 'Analog calculators, no batteries needed.'
I would freak out the really curious by handing them my Series 1 Curta 'pepper mill'.

Mine is wood. Still have it.

Bill_de Loc: US

clemente21 wrote:

Most of us know that 22/7 is the conventional rational approximation to Pi, but it is only good for two decimal places.

If you need more precision and do not have a calculator with the constant, using 355/113 will take you to about six decimal places.

My 'Windows' calculator goes a bit further. 3.141592920353982

You will sleep much better tonight knowing this.

---

Longshadow Loc: Audubon, PA, United States

Bill_de wrote:

My 'Windows' calculator goes a bit further. 3.141592920353982

You will sleep much better tonight knowing this.

---

BBurns Loc: South Bay, California

Bill_de wrote:

My 'Windows' calculator goes a bit further. 3.141592920353982
You will sleep much better tonight knowing this.

My Windows Calculator is better that your Windows Calculator.
3.1415926535897932384626433832795‬
I'll sleep not caring either way.
πR² is incorrect. Cake are Square, Pi are Round.

wrangler5 Loc: Missouri

Our high school store sold Picketts, so that's what I used, back in the '50s. Still have it, and bought a few more over the years. (Including a round Pickett I wish I'd had in high school, just because it would have been really cool.)

I kept one in the darkroom, where it was the quickest way to see enlargement ratios - set the slide, and all equivalent-ratio numbers are there without having to re-key anything. I still keep a short one on the workbench for when I just need 2 decimal place accuracy for something.

To keep it on topic: every general purpose slide rule I've ever seen has dedicated Pi marks on its scales. (Don't remember if the E6B slide rule I had when I was flying had a Pi mark.)

TriX Loc: Raleigh, NC

I had a K&E first and then a yellow metal Pickett. Loaned it to a cute blond and never saw it again 😩. I did learn to use every scale though (not just the C, D and CI). It was very useful for trig functions, right until the HP35 came out.