For Fans of the old HP RPN Calculators

[macdo]

One skill that is disappearing is the ability to estimate. Very often, I don't need to know a result to six decimal places; one will do. So, while some kid is busy entering all those digits into a spreadsheet, I would look at it for a moment and say, about 143 1/2.

You remind me of the vanishing skills of using fractions and simple proportion. The later not taught to my kids until I explained it to them as a way of getting a quick answer.

[houdini28]

One skill that is disappearing is the ability to estimate. Very often, I don't need to know a result to six decimal places; one will do. So, while some kid is busy entering all those digits into a spreadsheet, I would look at it for a moment and say, about 143 1/2. Five minutes later, the kid would announce 143.412745! Ok. But... ah... this voltmeter hasn't been caled in... ah... what does it say here?.... six years. I doubt it's giving microvolt-accurate readings anyway.

The other value of a quick estimate comes when you do need the answer to six places and the kid announces 173.412745. Ummm... check your numbers. I suspect you made a type-o. The answer should be closer to 143. When you reduce numbers to keystrokes, that can happen.

I never cared for RPN (Please don't throw things!), but learning how to use a slide rule was the best math education I received. Learning to quickly approximate, keep track of decimals, use proportions & ratios, and understand significant figures has served me better than the various advance math classes I had. After learning to use a slide rule, I not only came up with answers, but I understood them too.

[Esav Benyamin]

I wish I still had my circular slide rules, but at least I have the small one my brother gave me. I hauled it around so much, the leather sheath wore out, and I had Ken C. make me a new one.

[Emanuel]

I wish I still had my circular slide rules, but at least I have the small one my brother gave me. I hauled it around so much, the leather sheath wore out, and I had Ken C. make me a new one.

My father has tried to teach me how to use slide rules like a dozen times over the years.

In one ear and right out the other each time.

[Esav Benyamin]

Slide rule history: http://www.oughtred.org/history.shtml

[wintermute]

Learning to quickly approximate, keep track of decimals, use proportions & ratios, and understand significant figures has served me better than the various advance math classes I had.

My high school physics teacher would drill us with Fermi problems. Great for learning how to estimate. The classic problem supposedly asked of Enrico Fermi was "How many piano tuners are there in Chicago?" If only I could get my hands on a Curta calculator, THAT would be awesome...

http://www.vcalc.net/cu.htm

[wintermute]

Weird double post. Sorry about that.

[Ray Allen]

My HP12c original batteries lasted over 12 years. The second set is still running strong. Can not tell you how many times I have lost it which would cause minor depression only to find it sometimes months later.
Great device.
Cheers...

[weaponeer]

Great calculators! I had one of the first HP35s when it came out in , what, '73? Then I got the HP45 when it came out, and the HP25. I was a working field engineer in the telecom field then and they were all very useful.

I bought an HP15c and HP12 financial calculator back in MBA school in '83 or '84. Still have them and still use them to this day. They are both right here at the side of my desk and I use them almost every day. I think I have only changed the batteries 4 or 5 times over the almost 28 years.

Edited to add: I also still have my old Post Versalog II laminated bamboo slide rule from engineering school back in the 60's! I have to admit I don't use it very much, but it is fun to pull out once in awhile and watch the young engineers eyes bug out!

[SkinnyJoe]

Here's another legend:

[Gollnick]

My high school physics teacher would drill us with Fermi problems.

It was my high school chemistry teacher, George Johnson, who really inspired me. He preached that you must not see a number as just a group of symbols, keystrokes. No. Numbers have meanings. They represent physical things. A weight, for example, represents the material being weighted. And this raises questions such as just how accurate the weight is, what unit of measure is the weight expressed in, etc. In chemistry or physics... or engineering, you must not separate the numbers from these other traits because you're not just doing math with theoretical numbers but are working with physical things.

He taught to always estimate before you calculate. You can catch a lot of errors this way.

He taught us about significant figures.

And he taught us to do "unit math" which is so important when dealing with numbers that represent physical things where you have units of measure.

He did not allow calculators. You either did all your math... and there was alot... by hand or you let him teach you to use a slide rule. His goal here was to expose you to the slide rule but, even more so, the underlying methods that the slide rule teaches.

I learned a lot of chemistry too.

He was one of the greatest... won the Dow Chemical Catalyst Award as best high school chemistry teacher of... as I recall... maybe... 1978.

[Gollnick]

Here's another legend:

Yeah, yeah... but it's got "that key" in the lower, right-hand corner... the unnecessary key.

[Esav Benyamin]

Lower right?

[SkinnyJoe]

I have this one. Probably my all-time favorite.

[Ultraman]

I never cared for RPN (Please don't throw things!), but learning how to use a slide rule was the best math education I received. Learning to quickly approximate, keep track of decimals, use proportions & ratios, and understand significant figures has served me better than the various advance math classes I had. After learning to use a slide rule, I not only came up with answers, but I understood them too.

Old joke: Did you hear the one about the engineer who had a problem with constipation? He worked it out with a slide rule.

[Gollnick]

I have this one. Probably my all-time favorite.

Same problem... only they made it bigger.

[SkinnyJoe]

I remember borrowing my dad's HP once for an exam in the 1980s. The "missing key" sure made me nervous.:

[Phydeaux]

The first calculator I used was an HP-80. My friend's dad worked for HP and had one that we learned how to use. When I tried using a standard calculator, I didn't know what to do with the extra key...

Although i have gotten better using standard algebraic notation over the years, I am still faster using RPN.

Ric

[Gollnick]

Although i have gotten better using standard algebraic notation over the years, I am still faster using RPN.

Everyone is.

If I have to use an algebraic calculator, even just to add two numbers, I have to stop and concentrate really closely on just keying the math into the calculator. I think any extended session would give me a splitting headache. RPN is just so much more natural... of course, you have to actually understand what you're doing; you can't just blindly key in the equation and press that silly key.

[Phydeaux]

HP used to have a t shirt that had:

ENTER > =

on it.

If I am doing calculations on an HP and I press a wrong key, 99% of the time I can easily recover without having to start the whole calculation over again. With an algebraic calculator, I usually have to start back at square one.

Ric