Slide Rule vs Calculator Showdown: Decilon & HP-35

I compare the Decilon slide rule to the HP-35 calculator.

[@thomasgreene5750]

I used a slide rule in high school, and for about a semester in college in 1974. About 2/3 the freshmen engineering class had calculators. Partway through the semester, I bought a Texas Instruments SR-50 slide-rule calculator for $199.95. My dad was an engineer, had always used a slide rule, and thought the calculator an extravagance. When I was home for Christmas, he was giving me such a hard time about it that I challenged him to take it to work and try it. He did, and the first day he found that some calculations he expected would take an afternoon to complete took him about an hour. He kept using my calculator until I returned to school in January. He went out the night before and bought himself one. In the space of about three months the price had dropped to $99.95. I inherited his K&E 4081-3 and 4181-1 slide rules, and I keep them at my desk. My dad was a control-system engineer in the aerospace industry. In the late 1950s, he and a couple of other engineers designed the attitude-control thruster system for the Mercury spacecraft. He did the design calculations for that system using those slide rules.

[@EduardoBuenoamigo]

What a great story and what a great legacy passed to you. I am jealous, sorry. Growing up in Brazil my dad left us but I loved school and I loved math. I used the rule and it was not until college that I got a calculator. I was not crying because my father left, I was too busy being smart LOL. At age 11 I was working for an architect drawing hydraulic plants, even isometrically. He did the calculations, I just had to draw in pencil and ink over the structures, the measurement, and labels using an instrument we called "the spider". There were three parts to it: the sliding pin, the needle, and the pen. The sliding pin helped me align the guide with the drawing surface, the needle indicated the position of the selected character, and the pen allowed me to trace the characters onto the drawing. In a long story, you would know that my work with him got me my Citizenship in the best country in the whole world. I kept that lettering instrument, the pens, and the sliding rule to this day. Thank you for your story. Reading it was like watching a movie. I pictured the whole thing in my mind. You were so blessed! I hope you are doing well.

[@markjohnson4031]

Wonderful demonstration. Obviously, the HP is faster and has additional precision. Though the slide rule had fewer digits of precision, it is astonishing to me that few today even know the slide rule ever existed, even though they were the bedrock of engineering for 100 years and everything in the industrial age, the space age, and the computer age was initially developed with a slide rule -- including every building, bridge, ocean liner, railroad, or highway. I believe that the deep understanding of math is far better with slide rule use. The lack of precision was balanced by the fact that you learned to simplify your equations BEFORE using your slide rule for the end result. Also, to properly place the decimal you have to mentally estimate the order of magnitude for the answer.

[@738polarbear]

Mark Johnson Bravo Well said . Your observations are as profound as the knowledge of maths needed to use a slide rule.

[@gyroninjamodder]

>few today know the slide rule even existed That's because it's useless due to the small amount of things it can do and the complexity to use. For example your slide rule isn't able to more than one operation at a time, nor is it able to solve things like systems of equations. Electronic computers can be scaled massively which allows us to run simulations to test what we've engineered. Good luck running a simulation with a slide rule.

[@dannygjk]

@@gyroninjamodder Yeah but you need an app to do a couple of things you mentioned. With a slide rule and appropriate knowledge that's all you need. I love using computers I even spent a lot of time programming over the years but simplicity also appeals to me.

[@gyroninjamodder]

@@dannygjk To do anything with a general purpose computer you need an application. It's a downside that you can't add complicated applications to a side rule.

[@noth606]

gyroninja ignorance should never be justified. And that's what it is, no amount of blowing smoke up people's behinds will change it.

[@Mark16v15]

I'm probably one of the few who got to experience the death of the slide rule first hand which happened in the fall of 1977 when I was a high school senior. My father was an engineer so I was a little familiar with slide rules. He showed me a little how to multiply with one, but since were not allowed such calculation aids in junior high, I didn't pay it much attention at that time. Even in high school, it wasn't until your senior year when you're taking chemistry and physics was there a real need for such a calculation aid. So during the second semester of my junior year, Texas Instruments came out with their TI-30 for only $25 (about $136 in 2019 dollars, and cheaper than a good slide rule). My father bought me one. It was almost magical. A calculation that would have taken me several minutes if not an hour (assuming I got the answer right), took less than a couple of seconds. My high school offered a slide rule class which normally was attended by seniors who were planning on taking upper level science courses. But in 1977 a kind of announcement was made that I had not ever heard before concerning any class. Over the PA system for the first two weeks of the school year, the announcer practically begged for just a few more students to enroll in the slide rule class so that they could have a class. I found out later that they had a few enroll, but not enough to justify a class, and eventually cancelled the the class, and never had another one. Honestly, I couldn't figure out why anyone would want to waste time in such a class, when a calculator made calculations so much faster and even more accurate. Later when I went to USAF pilot training, I learned to use a flight computer, which was a circular "slide rule", and thus used the same principles of the slide rule to perform distance, speed and fuel calculations. So I did end up getting a little formal training (even that thing soon went the way of a comparable calculator device). Fortunately with YT, when I'm curious how those slide rules worked, I can always check out a video. How many other "deaths" have we experienced? Do you remember the first phone you bought that had push buttons instead of a rotary dial? Do you remember the first time you decided NOT to buy a landline phone service, and just use your smartphone? Do you remember the first paper you wrote on a word processor instead of on a typewriter, and thus quit buying Whiteout?

[@AureliusR]

Actually, in flight school today they still have you learn the basics of using a flight computer. It can save your life if all your electronics go for some reason. Always good to have a backup!

[@Zestyclose-Big3127]

"How many other "deaths" have we experienced?" My dad handed me down a HP Calculator so attempts to lend it out were fun. My parents also used a CRT TV in their bedroom until not too long ago. my computers still all have a VGA port. I don;t know how long I can continue to say that. growing up I had a PC with a floppy slot. Floppies were long outdated by the time it was actually bought though

[@ProfessorHerning]

I'm not a pilot, but I have one of these for a future episode of I ever have the time.

[@TonyDiem]

Still have one, but a film camera, and now even more just a camera. I recently bought an A6500, but that is more hobby stuph for me. So firstly, film camera, secondly even a digital camera. Oh and then there were the disposable ones too. I took a panoramic disposable with me to Antarctica in 1993.

[@toomanyhobbies2011]

Awesome comment! Sums up the entire idea of obsolescence. It's not a bad thing, just the way things work out.

[@kevinurben6005]

Before calculators, if you needed more precision than a slide rule you could use log tables, which included log tables for trig functions.

[@smitajky]

In computing the permittivity of free space I needed 15 figure precision. No slide rules, no calculators, no log tables, no computers. Oh bother. Page after page of long multiplications, long divisions and the long division method of square roots. Not easy.

[@amoledzeppelin]

No computers? That's a shame because dc and bc have existed on normal OSes for ages, and they allow to adjust to a very high precision.

[@cigmorfil4101]

​@@amoledzeppelin But not prior to 1960.

[@Walkercolt1]

And if your took "Statics and Strength" in college, you also had "The Brown's Book of Materials" in your shirt pocket and a CRC "Handbook" under your arm. The leather covers of my "Brown's" have fallen to dust and my used CRC Handbook's pages are also fragile as the Dead Sea Scrolls. I'm 70, and I was 17 when I bought them both!

[@MattMcIrvin]

There were also mechanical calculators with many-digit precision, but the best even the most expensive ones could do was the four basic operations and occasionally square roots.

[@OleJoe]

My HP 35 is in a land fill somewhere. My K&E Deci-Lon is still like new in its leather case, ready for use.

[@Patterner]

i still have all my HP calcs. i

[@KB4QAA]

Takes me back to high school, and yes we had speed contests with HP-34. I felt that I had a better grasp of mathematics when using the slide rule that was lost when I got a calculator. Using the slide became intuitive and satisfying like playing the piano.

[@ProfessorHerning]

The downsides of electronic calculators really show over time. Many of my students have a poor understanding of arithmetic, magnitude, and numerical relationships. They aren't forced to think about them. On the other hand, I think my own numerical skills have improved since picking up the slide rule, especially approximation. These days in class I always find myself giving a quick numerical estimate of a (exact) solution in class where in the past I would have used a calculator/computer or just skipped an approximation.

[@KB4QAA]

p.s. It would be helpful if you write down the intermediate calculation figures as you work through the problem! cheers. b.

[@ronvonbargen8411]

I agree. I work as a machinist (30 yrs now.) But when I first couple years after I started my career I had a little orange book with all the trig tables and formulas in it and I would do all the math with a pencil on the blue prints (they were actual blue prints then) them one day my boss came out have me a calculator and said quit scribbling all over the prints. Now e have cnc and c.a.m. System that does all the math for you. Don't even use a Calculator hardly.

[@timmiller7524]

In the early 70s as a student I had a Pickett & Eckel slide rule made in Chicago. I still have it and use it to keep my skills sharp at 75. The slide-rule requires the user to think. The calculator started the general decline in mental arithmetic that has brought civilisation to its innumerate knees

[@pnachtwey]

My HP-35 still works. It is two feet from me now as I still use it. It is from about my freshman year in college which is form about 1971-1972. It really help to pass exams. My battery pack has died but my HP-35 still works while plugged in. I liked the HP RPN because I didn't need to mess with parenthesis. I also didn't need to mess with second buttons. My HP-35 cost about $400 when I bought it. That was a lot of money for a pathetically poor college student.

[@jacquespoirier9071]

I done my engineering classes with a slide rule, this was many decades ago. When I retired, I done a demo of that process to my work mates, they were in computerized calculations and drawing systems. When we consider that all the calculations were done that way, this deserves all my considerations. very good demo, that reminds me something very good video

[@kwgm8578]

In 1973 as an undergrad my girlfriend owned a calculator that did the 4 arithmetic ops and had a sqrt button, which was great for calculating the hypotenuse of right triangles. It also had 9 or 10 significant digits -- way too many for anything we needed to do. That calculator cost her father ~ $350.

[@martinfiedler4317]

That's what lots of modern technology boils down to still: Useless features for horrendous amounts of money...

[@TonyDiem]

I just took a Lean Cert class, and we could only use a 4 function calculator (or turn off mobile data on our phones), I bought my coworker and myself one each for less than $2, and they had solar. That's just crazy.

[@donpanton9250]

Nice, but too many aaaaaahs. Maybe you Americans learn to narrate? It´s like like like like….. But overall like neat ;-)

[@spinav8r]

@@donpanton9250 Thank you! We like, uh, didn't, uh like, know that. You're, uh, like uh, some kind of, uh, bloody wanker. Just in case you didn't know that. You're welcome. By the way, notice how I didn't address a whole group or nationality of people. Nope, just you, Knob Head. Cheers!

[@jeff2tc99]

My girlfriend had a hp-25. I tried to convince her to swap for my hp-21. (Eng students were ruthless). In the end I bought one with my early pay checks. In those days in Australia, a small “desktop pc” was reputed to cost the annual salary of a graduate engineer. I only used one once for a frame analysis - hourly rate was prohibitive and resorted to hand calls.

[@JerryEricsson]

cool video. In 1973 I was a soldier stationed at Fort Bliss Texas with the 2/3rd Armored Cav. I was a sergeant Field Wireman. We had our commo section in a brick square building at the motor pool, our Captain had one of those calculators and spent hours playing with the damn thing when he should have been taking care of business. I thought the calculator was cool but as a Hs dropout with my GED (needed to get my Sgt stripes) I had no idea what the thing was capable of. Watching these type of videos, I went online and picked up a cheap slide rule, think I paid around 10 bucks for it, used of course almost identical to the one in your video in a nice leather belt case. I can do multiply and division with her with ease, fun to see the other things she is capable of. I did get one of those calculators as well in a box of junk for 15 bucks from a police auction, so I now have both devices but my computer does it all for me with so much greater ease. How time changes our abilities.

[@ghlscitel6714]

1973 I bought my first HP calculator in Geneva. That time I was visiting CERN as a student. Was really happy I got rid of the slide rule and log tables.

[@alandaters8547]

I used my father's K&E slide rule(from 1927!) in H.S. in 1969-1969. This sure brought back memories! (Still have the K&E, but the leather case is beat up.) Thanks for the video!

[@philipwakeling2777]

I started engineering school in 1972. I picked the HP35 (and still have it, although these days I use a HP48GX). In high school I used a Faber-Castell trilog slide rule. As I recall, the HP cost $228 in bulk. 50 of us first years got together to place the order directly with HP.

[@aljawad]

A great demonstration of personal computing devises from yesteryears! I collect slide rules, and still use them both professionally and just for fun. Often I like to confuse people who have never seen one - for example at restaurants I’d pull one out to calculate the proper tip (sure, I can do that on my Apple Watch, but where is the fun in doing that!). Alas, today’s young student who do their homework using Wolfram Alpha (an awesome tool, BTW) on their smartphones and tablets can have no comprehension of the beauty of performing arithmetic the old fashion way!

[@MichaelBernhardArpSrensen]

Great video, thanks. I allready collect slide rules and HP calculators, so this video is a real treat for me.

[@machintelligence]

Oddly enough so do I. In high school I used a Post Versatrig slide rule and in graduate school I bought an H-P 45 new. ($400.00 -- in 1974)

[@noferblatz]

In 1975 (when I graduated high school), the HP 35 was selling for $300 - $400. I had a friend in my chemistry class who had one of these his parents had bought him.

[@garynakanishi981]

Yes, $395.00 in 1972 I was working for minimum wage at Dole Cannery for $1.60 an hour. If I worked for 300 hours (after taxes and starving [lol]) then I could buy one and hopefully not have it stolen or damaged.

[@fouellet1701]

When I was in high school and college in the mid-60's the scientific calculators were making their debuts and were horribly expensive... so we all used slide rules that cost a few dollars. I later bought a Commodore scientific calculator in the mid 70's that still cost a fortune, compared to what we can get today. Great fun.

[@okaro6595]

In the late 70s they were relatively cheap, The Casio fx-39 I had was about 200 FIM or 115 € adjusted to inflation (200 € adjusted to wages). Of course that still was up to 10x the current prices but back then they were high tech comparable to smart phones now.

[@ironcladranchandforge7292]

Still love my Mannheim Acu-math slide rule and practice on it regularly. It works the brain in my old age, LOL.

[@GoSlash27]

Minor quibbles: 1) The increased precision of the calculator implies increased accuracy, which is false. No result can be more accurate than the data that was used to generate it. 2) The slide rule is much faster for computing 2a) fixed ratios applied to multiple values such as conversions 2b) chained functions... provided you can keep the decimal point in your head, and 2c) solving complicated equations for which the slide rule was specifically designed (such as the Tsiolkovsky rocket equation, ballistics ranging, reactance/ resonance problems, etc). There are some jobs where a calculator is more handy or even a spreadsheet (assuming a computer is available), but at least in my line of work there are many cases where a slide rule is the quickest and easiest option. Very nice presentation!

[@robertromero8692]

Any good engineer knows about limited precision. You NEVER see answers on an engineering test given in a lot of significant digits.

[@GoSlash27]

@@robertromero8692 Precisely! (pun intended). The accurate answer to both the above problems is only the first 2 digits rounded since that was what the problems provided. Anything after that is meaningless. We don't know if the length of the hypotenuse was exactly 83.0000' or somewhere between 82.5000' and 83.4999'. Too few calculator students were taught the difference between 'precision' and 'accuracy'. In most engineering fields, 3 digits of precision is more than adequate.

[@SpinStar1956]

I was a junior in high school when I got my HP-35. The HP-45 had just came out and was available. I just could not allow my Dad to pay the extra $100 for the HP45. However after learning more, I wish I would have with some proviso to have paid him back. The reason is the HP-45 had rectangular-to-polar and vis-versa; along with memories and other conversions and functions. As the NASA space-race was in full swing, HP made the sales-claim that you could "Calculate your way to the moon and back." with the accuracy it had! The Hp-35 had just dropped from $395 to $295 with the HP-45 taking the $395 spot. The only place that you could get these was at the local college's bookstore, and they sold fast even though it would just about break your (or your parents!) to afford it. I was amazed that back in the day, most all of my professors allowed calculators even though most students were still using slide rules; I suppose they were more concerned about methodology than digits-of-accuracy! Mine is still in use today and I was able to get an HP-45 so all is good. Finally, I was able to get the great HP-67 with its programming and magnetic cards. I still use these calculators to this day exclusively everyday! They have held up well and with very little maintenance. Even today they will do most all you need for a working engineer...

[@Justmyopinionlol]

Thank you for this demonstration. My grandpa told me to learn how to use the slide rule on youtube for my apocalypse kit I am putting together.

[@marcmiyamoto]

Is this sarcasm?

[@samisiddiqi5411]

Based. I've been trying to decide between Four Function and Slide Rule but I'm already so competent in math that I don't think I'll need sine or cosine functions to make trig calculations... I do wonder what your kit is...

[@fireblade95]

What else is in your kit , for the love of God please let us know....

[@jamestamu83]

In junior high my friend brought his dad's HP-65 to class for "show and tell". You could insert a magnetic strip into the side of the calculator and it would pull it through, reading a custom program. This was circa 1974. It created such excitement! It was like the first Apple iPhone of the day!!

[@tkarlmann]

You don't "pull" the memory card through the HP65, you set the card in the slot, give it little nudge, and a motor takes the card through the device.

[@alexandredeoliveirapenna198]

For the price tag at that time, slide rule for sure.

[@rbeehner2]

I worked in a consulting engineering office in the mid-1970s and began with the same slide rule. We couldn't actually afford the HP Calculator but aspired to own one. Our experienced engineers showed they were faster and as accurate as the calculator. But, there was one other resource we used Smoley's three or "Smoley's four combined tables." A very fast and accurate way to solve Rise, Run, and Slope. Eventually, I did buy an HP-35, and fifty years later (when I retired) I still preferred the entry speed and logic of using RPN.

[@gerardtrigo380]

I will tell you what I did pick, both. I had both a Dietzgen Manheim Slide Rule and K & E Duplex slide rule and in 1974 i bought a TI 50. Before 74 the University would not allow the use of calculators in class rooms or for tests. Sadly, beyond basic multiplication and division, I know longer remember how to use a slide rule. Though when an undergraduate I had the reputation for being fast and accurate on the slip stick. My biggest problem back then was keeping track of the power and decimal point.

[@lenkapenka6976]

Superb video, much appreciated! Greatly educational even for those of us schooled in the 1980's!

[@mikehunt3205]

"If you're taking a three hour boat tour, take a slide rule; trust me on this." - The Professor

[@thomasgreene5750]

And a good-looking actress.

[@InAMinMaths]

Great video. Using that calculator and a slide rule are lost skills now that virtually no one would know how to work. Thanks

[@DavidGarvinTechnophile]

I have a K and E Decilon that I recently purchased. I am learning to use it and your videos have been invaluable.

[@KB4QAA]

By the by, I was given my first slide rule in 5th grade, around 1970. No teacher ever objected to me using one. I had several, mostly student models. My favorite was a pocket Sterling that was quite accurate and easy to read. It broke just as calculators were first becoming common. The only replacement I could find in my small town was a Post 10 inch student model that was quite crude and rather inaccurate even for my high school physics class. That prompted me to get a TI-51 calculator that took me into college; cost about $55; $241 today!!!! However even in 1979 there were still grad students and professors carrying slide rules on their belts.

[@ProfessorHerning]

Pelican1984 interestingly, Problem 2 would be a little hard on an SR-50/51. You'd have to calculate the exponent and store it in memory explicitly.

[@donmoore7785]

I was in 5th grade in '71, and we never learned to use a slide rule through my high school years. I don't recall having a calculator, but it seems like I must have. I do remember well having one right off the bat in engineering school in '79. Only now after all these years, have I learned the basics if using a slide rule. I have to go find my dad's - he worked at Bell Labs from '27 to '69, and certainly he used one constantly.

[@gbennett58]

I entered university in 1970. I began using slide rules in high school. My first calculator was the TI SR-10 in 1973. From 1975 to 1979, I was using an HP 65. After that I had an HP 41C. Everyone had calculators. After about 1973, slide rules seemed to completely fade away. In 1979, I can't remember a single student or professor using a slide rule, it would have seemed really unusual, like riding a horse to work instead of a car.

[@kimchee94112]

You could tell an engineering student by the way he carries his slide rule attached to his hip like a Samurai.

[@sjpbrooklyn7699]

In 1959 my high school geometry classroom had a six-foot long demonstration slide rule mounted on the wall above the blackboard. My own slide rule which I still have is a DIWA (Danish) Polylog with 12 scales on one side and 10 on the other. I don't think I ever learned how to use more than four of them. By 1964 my undergraduate physical chemistry lab at Ohio State began to replace mechanical calculators with an electronic desktop model (ANITA made by Sumlock). In 1975 I bought an HP-35 to do epidemiological studies with, and of course learned RPN. It was tedious but necessary when I had to do calculations at home without access to the Cray CDC 6600 computer. However, the revolution came when HP released a calculator with similar features but with a small programmable rectangular magnetic strip you could feed through. In 1979 A scientist at the National Cancer Institute, Ken Rothman, published a game-changing book called Epidemiologic Analysis With a Programmable Calculator with listings for dozens of standard biostatistical procedures you could program on the strip once, then run with your own data sets.

[@W4BIN]

I had a Lafayette "log-log deci-trig" slide rule made of bamboo & plastic (it looks very much like that K&E) in 1960 until 1973|1974 when I bought a hp-45 calculator, after a good price drop. Besides having to learn the slide rule to use it, the slide rule is not 100% repeatable like the calculator is. I was taught to put a high dot to indicate multiplication or just leave a space, not a "x." I have a small slide rule collection from Goodwill. Ron W4BIN [now retired]

[@donmoore7785]

Excellent presentation. Educational. I never stopped to think about what the precision of a slide rule may be. But it appears to me that is was sufficient for most tasks.

[@oldbutstillcurious3615]

Would have been if my answers were anywhere near correct !

[@Rocketman88002]

Man this brings back memories! I remember the days we weren't allowed electronic calculators in college. Besides the simple 4 function ones with red LEDs there was the HP35...a scientific calculator. Then came the Radio Shack, Sinclair and many others. The good old days!

[@MattMcIrvin]

Around 1976, my father bought an Omron 86SR (I think the SR was for "slide rule"), which had basically the same scientific-calculator features as the HP35 but was less capable in that it only showed 5 significant figures when it was showing the exponent (or 8 without). It did have a radians mode. But it was also quite affordable. He liked it so much that he got me one too. I didn't understand all those transcendental functions at the time but I would eventually. It had an appealing chunky design with big round buttons, actually no more buttons than a simple four-function calculator but it had a shift button that accessed all the advanced stuff. The display was a blue-green VFD, pretty power-hungry. It lasted me until the mid-1980s, when it stopped working after taking a fall.

[@michaelturner4457]

This is the sort of video I have on when I can't sleep.

[@amoledzeppelin]

That Decilon is quite a beast. But a pocket circular slide rule like KL-1 is one love.

[@jadenephrite]

Regarding 3:34, the price of a Deci-Lon 68-1100 slide rule in 1965 was $22.50 which would be equivalent to $182.96 in 2019. The Hewlett-Packard HP-35 was introduced on February 1, 1972 for $395 which would be equivalent to $2,420.49 in 2019. Their down side was their LED display consumed such battery power that they had to be recharged often. It was not until 8 years later in 1980 that LCD displays were developed which consumed less battery power such as the Texas Instruments TI-30. Seven years later in 1987, solar cells provided power in an ambient lit environment such as the TI-30 SLR+. Nowadays scientific calculators are inexpensive costing around $11 which would be equivalent to $1.80 in 1972.

[@hifijohn]

Have owned a few HP calcs, they were great very well built and very reliable but they were insanely expensive.

[@michaellyons1313]

Thank you for listing/explaining the true price. I still have my HP-35 that I bought in '72 for $395, as well as my HP-45 that came out a year later. They both still work perfectly....as does my Post VersaLog II. :)

[@machintelligence]

@@hifijohn Price is a relative thing. I passed on the H-P 12C business calculator in 1981 and bought the TI 35 business for about 1/4 the cost. It died (keyboard) four years later, so I bought another and four years later it failed too. By that time the H-P was under $ 100 so I bought one. I still have it and it works flawlessly. The H-P 12 C is still in production today and is a standard of the real estate industry. Not bad for a 40 year old design.

[@jondrew55]

In 1973 I was a freshman in college. It was the first year my school allowed the use of calculators as opposed to slide rules. I was lucky enough to get an HP-45. Our first physics 101 lab was basically nothing more than calculating a large amount of measurement data. It normally took a full 4 hour lab session to finish the calculations. We did it in 45 minutes using the HP-45. Our professor was not amused and announced he’d be spending the next few months making that first lab more challenging for freshmen. As I recall, the HP-45 was either $400 or $450.

[@tchevrier]

wow!!!! I haven't seen one of those calculators in years. When I was in high school I used to have an HP 65 with the belt pouch. Love that reverse polish

[@ahbushnell1]

In 73 I took the first circuit theory course. In my final I was doing complex number calculations using a slide rule. I ran out of time and did not finish the test. About that time the new HP34 was available. It was $400. I got a summer job with Shell and used a good fraction of that money to buy a HP-45 which came out that summer. Big game change.

[@Roger-go6jc]

God, that took me back! I grew up with the slide rule and got a Sharp calculator not long after the HP you're using. But I always tended to reach for the slide rule.

[@MBJanus]

I had a slide rule Graphoplex in the late 60's. If I was told that some years later I will have such a calculator I think I would have put it in the backyard, near my rocket. Seriously, for acurate results, we used a little book with log and trig tables.

[@davethomson5921]

Brings back many memories of the transition from the analogue to the digital age. A rather nice example of when the slide rule can give a very much faster solution to a problem than pencil and paper or a calculator is this: sinθ=cotθ. Find θ. This can be solved on paper with some trig and quadratic equations - and has nice links to the golden ratio φ. On a calculator you can use an iteration to home in on the answer, but it takes a while. On a trig slide rule, especially if there is a red cot scale, you can find the answer in a couple of seconds. I leave the problem as an exercise for any interested reader. Is there any faster way of solving this?

[@Raison_d-etre]

This is why you want a calculator with a solver function.

[@cigmorfil4101]

​@@napoleonbonaparte640 Especially since there is a direct square/square root across the slide, requiring only the use of the cursor.

[@imlassuom]

So this is the slide rule...impressive!! I did not expect that it can do all of this.

[@BertGrink]

An electronic calculator has at least one advantage over a slide rule: once you are familiar with the layout of the keyboard, you can operate it in total darkness! ;)

[@DanHaiduc]

You might be able to operate one, but if it's LCD without backlight as cheap ones come today, you will not be able to read the result.

[@tinymonster9762]

In the 1980s Hewlett Packard did slide rules for microwave engineering for calculating reflection and transmission parameters for waveguides. We all had them, they were essential. Even today they are relevant, fast, accurate and ridiculously easy to use. I ended up with a handful of variations and they were always in demand.

[@markbratcher9095]

I remember when the calculator revolution really took hold. I was in undergraduate college in Cleveland, OH from 1974-1978. In my sophomore year, about 90% of the engineering students used slide rules. The following year, this practically reversed to about 90% with calculators. I suppose one could correlate this with the availability of certain new calculators in that period of time at price points that made them more accessible. A funny thing happened in January when the Civil Engineer students were outdoors for some lab work. Their calculators wouldn't work because it was too cold, so they had to use a slide rule anyway. :D

[@chet3030]

So your sophomore year would've been fall '76/spring '77? That jives with the fact that the much less expensive Texas Instruments TI-30 (MSRP of $25 at the time) was introduced in 1976. I think that's why you saw such a turn around in calculator use the following year when the TI-30 had a year to get popular.

[@Mandragara]

Makes sense as a calculator gives you such an advantage in a timed exam compared to a slide rule. Tech up or lose

[@markbratcher9095]

@@Mandragara actually, back in the day of slide rules, people were good at them and the time to perform the typical calculations on a slide rule was competitive with doing it on a calculator. The calculators, though, were more convenient in terms of being more compact and, ultimately, had more capability such as memory and a wide variety of trig functions, etc.

[@tonyb83]

Back in 1972 when I was a young civil engineer useing a slide rule I decided not to buy a calculator because I didn't need the precision it provided AND they were far too expensive for my needs. Later when the cost of calculators tumbled down I still used my slide rule because it was accurate enough. Eventually I bought a scientific calculator........but I missed the feel of using a slide rule, its much more satisfying than pushing buttons.

[@ivorybow]

I would have chosen the slide rule simply because of cost. Slide rules were a mystery, because in my day, girls were not allowed into the physics and higher math classes. I'm getting my revenge now because this grandma just purchased a vintage slide rule and I am learning to use it. By time I was in college, calculators were affordable, though we were strongly discouraged from using them, and had to demonstrate during exams we could do long hand math. I had to learn long hand square roots...really fun! As an aside, my first serious job was in a petrochemical design office. We used the Smoley's tables and a hand lever crank calculator which produced a paper tape with answers.

[@oldtechie6834]

On a HP-35, the power raising function is 'x to power y' while on a HP-41 it is 'y to power x'.

[@rhymereason3449]

I'm old enough to have taken a slide rule course in 9th grade in prep for sciences in HS and college - but it still amazes me that we basically went to the moon and back, and designed the 747 with slide rules and one or two significant digits of accuracy.

[@timmiller7524]

Not so. For high precision many industries had rooms full of comptometer operators working round the clock. Before that the same thing was done with trig and log tables. No-one who went to the moon on a slide-rule ever came back in one piece

[@protosfotod2416]

No one ever went to the moon btw. Research...

[@rhymereason3449]

@@protosfotod2416 You couldn't bounce a LOW POWER laser off the moon without the reflectors that were left there... and that's been done many, many times.. any college physics class can do it.... sad that your critical reasoning ability seems to be non-existent...

[@protosfotod2416]

@@rhymereason3449 an experiment bought to you by the Rockfeller and Goverment sponsored university? You dont see the conflict of iterest, or you do not want to see it?

[@protosfotod2416]

@@rhymereason3449 nope

[@markbratcher9095]

When discussing precision, one should note when it's meaningful. Many inputs to calculations only have a few digits of significance to start with (e.g., if you're entering values of electrical components, they have tolerances quoted in their specs, or if you measure the length of some objects, your measurements are only good for 2 or 3 significant digits). A slide rule maintains good accuracy when dealing with 3 to 4 significant digits. With a calculator, you put those numbers in and make a calculation, you get a very "precise" number (10 significant digits) but it is only accurate to ~3 significant digits in that case. The rest of the digits are useless.

[@robertromero8692]

Sure, but better to have too many digits than too few.

[@markbratcher9095]

I certainly would want to lose digits that are meaningful. But whatever digits you have, you must know the true precision of the value.

[@robertromero8692]

@@BuildTheFutureYouWant The fault would lie with the engineer interpreting the numbers, not the calculator for showing more digits.

[@robertromero8692]

@@BuildTheFutureYouWant Any competent engineer would know to round off to only the measured precision. This is strongly emphasized. When I took the PE exam, people used calculators, but the answers to choose from were always given in only three or four digits of precision.

[@amramjose]

I enrolled in a 1 credit slide rule usage course my 1st semester of college, which was cancelled before it even met once. Immediately after, I purchased a TI30 for a hard earned $30, which was followed by a TI51-II (I think) then by my favorite HP35e, which took me through engineering school. It was simple, had volatile memory but it was excellent. Now my go to calc is an HP35s. Other than eating batteries, it is excellent (not as good as the HP11 or HP15 but it will have to do). My next calculator may be Swiss Micro 15 or the 42...RPN rules!

[@thomasgreene5750]

You can get a free emulator for most HP calculators that runs as an app on a smart phone and uses a touchscreen image of the calculator face for input/output. I used an HP41CV for years and switched to an emulator of it when I got a smart phone. I haven't carried a calculator around since.

[@andyk9685]

A fantastic time travel for me. Thanks !!!!

[@gbennett58]

I started out using a slide rule. My first electronic calculator was the Texas Instruments SR-10. I could never reliably keep track of the decimal point with the slide rule. Since the electronic calculator removed that problem, it was for me the biggest improvement over the slide rule. The extra precision was nice, but the decimal point was the bee's knees.

[@kimchee94112]

Actually keeping track of the decimal point will sharpen your mind. You will develop a feel for the answer if the decimal is off. With a calculator you mindlessly assume it's correct.

[@Greatdome99]

I went all the way thru graduate school with a Post Versalog slide rule. I got a HP35 in 1973 which came with a genuine kid leather case. We got them at a discount since HP was right up the street, and some of our coworkers spouses worked there. Texas Instruments had a comparable model then too--though not Reverse Polish Notation.

[@JLoud66]

I remember being amazed seeing the Hp 35. I was 14 and got a summer job working for a surveyor who had one. It was super expensive but his pride and joy. They also had an IBM 360 computer which was also amazing. I remember one of the guys who was programming that computer for a project with the punchcards. He saw I had a small 6 inch slide rule and asked to use it because it was easy to estimate data points to smooth out the plots the computer was creating.

[@johncolvin2561]

The answers that one gets using a slide are accurate enough, one only needs three figure answers for almost any work, even today.

[@transmaster]

I too watched the death of the Slide Rule. I remember using an HP-35 for the first time. I remember muttering to myself 9 significant digits, 9 significant digits, 9 significant digits, To this day I only only use HP's and RPN notation. I now have loaded into my iPhone all of the HP calculators in emulation, including my all time favorite the HP-45.

[@kimchee94112]

No slide rule or calculator needed. My chem professor had log and trig tables in his head and did all the calculations without paper and pencil. There were 300 of us, the next class day he knew everyone by name. Enrico Fermi calculated in his head for the first nuclear energy released in real time on the Manhattan Project beating the computer.

[@JamesBoddie]

Still have mine (since 1972). It taught me to use RPN and I use that with the calculator app on my phone.

[@DirtyLilHobo]

In 1972, using slide rules and massive mechanical calculating machines working for the Bureau of Reclamation, I saw an HP-35 and HAD to have it. I paid an ungodly price of $380 dollars and was simply astonished at what it could do. It also played musical interference in the AM band. Texas Instruments also had a similar calculator for around the same price. An amazing device at the time but is now far surpassed by other devices. I still have the HP-35 and its original case but sadly no longer functional.

[@kimchee94112]

TI SR-50 half the price. I have two of them, both dead but my HP still going strong.

[@EtzEchad]

The one case where a slide-rule wins is when you want to do several calculations using the same number so you don't have to move the slide. For instance, if you want to make a table of numbers multiplied by pi. Then you can just set your index on pi and read off the numbers.

[@beckettparker2395]

it is the showdown of the century... the one we've been waiting for...

[@jeff2tc99]

I powered through 1st year engineering in 1974 with a slide rule. In 1075 I bought a hp-21 (I recall it was AUD200?). Still can smell that guy. Brilliant. Lasted me several years till I bought a hp-25 for the programmability. It’s simple Progs help me through many years of high-rise building design. Love these little guys. I recall in 1975 they were banned in exams as not all students had them, but by 1976 all students had one of the many brands of calculator.

[@daveduncan2748]

I was in high school when they first started allowing calculators in math classes. I never understood why they tooks so much time teaching us logarithms that we hardly used for anything. I suspect it was mostly a carry-over from the slide rule age, when logs were king.

[@AntonioBarba_TheKaneB]

terrific video! thank you for sharing! I always wondered how to operate a slide rule, now I want one :D

[@jeffreyfrancis42]

Neat video, but I'll admit I spent more time marveling out how you're able to write while holding a pencil that way than watching the computation. ;^)

[@twinturbine320]

One of my classmates in my engineering course in the early 70's came in one day with a new HP35. We were totally blown away as we had all been slaving away with slide rules and a lucky few had the new 4 function calculators. We thought he must have been rich as the price was over $300 at this time. I generally didn't have a problem using a slide rule, except that you had to very carefully track the exponent so you knew where to put the decimal place in your answer. Re-checking your answer was a pain because the slide rule was so slow in a complicated equation.

[@joen7xxx]

Started Mining Engineering with a set of K&E Log-Log slide rules. Bought a sears calculator worth trig and log functions for $175 in 1974 for my underground surveying class. Still have my slip sticks but would be hard pressed to use them today for More than multiplication and division.

[@littleshopofelectrons4014]

I bought a HP45 in 1974 while in engineering school. I paid $395 for it. Prior to that I was using a top-of-the-line Picket slide rule. That HP45 was like science fiction! I never touched the slide rule again. I do wish I had kept the Picket though for nostalgic reasons. I still have the HP45 and it is in perfect condition although I did have to replace the NiCD battery pack.

[@douglasstrother6584]

I love having my Dad's K&E sliderule: I can keep working during California's rolling blackouts.

[@ericportillo8277]

All those scales on both sides!? Cool! lol

[@toryvaughan4940]

Thanks for the great video. I enjoyed trying to see if I could solve the problems you gave with the slide rule as fast as they could be solved on the calculator. The trig problem I managed to solve almost as fast as on the calculator but the calculator won with the exponential problem although I was not too far behind. Of course the accuracy isn't as great on the slide rule but it is still fun to be able to solve these type of problems with the rule. A big advantage of the slide rule is that you never have to worry about the batteries dying on a exam or during a important calculation.

[@738polarbear]

A great tutorial Professor . I remember that I couldn't wait to get my first calculator but I also Rembert going back to my trustee slide rule because it was so familiar to me , My knowledge of maths is far superior to my grandkids . Not because I am a genius and they are not slow but because in the not too distant past I believe subjects were taught better and teachers pushed you harder . They think you are a bully now if you force them along . Mankind is relying too much on machines without really understanding subjects in depth in my opinion . My daughter taught at university and she cannot belive how low grade the first year students are and she was only 35. Haha . Yes they do nit even teach cursive writing any longer . It is criminal really.

[@johnpawlicki1184]

It was important that, on physics exam solutions back in 72, that one only delivered the proper number of significant digits. More was essentially incorrect and most of my professors marked off signficantly for that. If one has constants and data values to 3 or 4 significant figures, delivering 10 digits was considered wrong. I drooled over that HP. Slip stick was still fast and a lot cheaper. ;-)

[@dougberrett8094]

RPN is the best system. Have used both. Once you wrap your head around RPN it is much easier than the other one. I had use of an HP67 before they were on the market. Wonderful way to learn how to program with limited steps. One thing that must be mentioned. I never had my slide rule malfunction, but did have the calculator blink out on occasion.

[@The4Crawler]

My 1st year on college, most classes banned calculators for tests, but the Physics 101 class allowed them. My friend had an HP35 and I had my dad's old Post slide rule. What was interesting was the test questions were still set up for slide rule solutions. You would do some hand work setting up the solution and many things would cancel or simplify, then you flicked the slide rule back and forth a few times and got the answer. But, my friend with his calculator started punching in numbers right away. I think we both took about the same amount of time to get through each test question. I did ultimately get a TI SR52 programmable calculator a year or two later. As mentioned in a comment below, you do get a better grasp of the math with the slide rule.

[@ericerickson6537]

In 1972, I started grad school and bought a TI basic calculator for $200 which at that time was a lot of money. But I thought it was great especially for my math stat courses. Then over 35 years of investment banking, I always had a HP 12c financial calculator which I used until 2012 when I retired. Now I just use my iPhone? I still have an old slide rule. I may get it out to see if I can still use it? Good video.

[@tubedude54]

I opted for the HP45 when I went to college in '73. Most had the TI's and Casios and were bewildered when I would loan them my calculator in class and it had no parentheses or equals sign on it...

[@timjackson3954]

I've still got my Aristo slide rule. Always thought it might come in handy for navigation at sea as a backup if my calculator gets wet. At college back in the day we used to do calculator v slide rule races, it was pretty even, mostly depended how familiar each operator was with their instrument. It is unusual in practical situations (physics lab) for the source numbers to have more than 3-figure accuracy.

[@thomasgreene5750]

I use a Concise circular slide rule to calculate time-to-waypoint problems at the helm of my boat when navigating in fog. It is compact, faster than any other device, and being circular, there is never a need to swap indices. I have one at the helm, and one at the nav station.

[@CristiNeagu]

0:08 OMG. Most satisfying focus ever.

[@pietergeerkens6324]

A true HP aficionado would have used the 76.2 still on the stack and keyed only an additional 27.6 tan * to get the y value of 39.8. That then compares favourably to the slide rule's efficiency. ;-) Great videos! Thank you. Although pretty good on a slide rule, I've learned several new tricks from watching your videos. Almost forgot: In 1972 or 1973 I replaced an expensive plastic slide rule with a Staedtler Mars 944 24 (that I'm now refamiliarizing myself with). My first calculator (4-function only) was only acquired as a free "gimme" for a magazne subscription in the late 1980's.

[@paulmoffat9306]

I bought one when I was in University, and that was before 1972 - it was rather expensive but I thought it was worth it (I still have it, still runs). Over the years, I had to replace the cells in the battery pack - they were Ni-Cad, (3 cells), and I changed them out with NiMh that were several times higher capacity. One thing to note, that may address their longevity, is that the circuit board inside is plated everywhere with 18K GOLD. With mine, in Physics class I could calculate a pathway for a spacecraft going to the Moon! I know Wikipedia states it was produced 1972-1975, But I had one a few years before then, as I had it in my first year, so about 1969.

[@garysheppard4028]

I never could get my head around slide rules. Had them back in Uni days just as calculators hit. Worked two weeks to save enough for a HP25. Pretty amazing for those days. But I still wish I could have understood slide rules. Just beyond me I guess.

[@calcaware]

I have a TI-2500 Datamath from 1971/1972. It can only add, subtract, multiply, and divide. There's a switch that says CHAIN/CONST, but even after looking it up I don't understand what it does. I love the design of it. A bit chonk, but looks really cool. Like an aperture science design.

[@LesBell]

Of course, just one year later, the HP-45 reduced the solution of Problem 1 to 27.6 [Enter^] 86 [Shift] [->R], using the polar-rectangular conversion function to immediately return x in X and y in Y. It's been in every HP scientific calculator since. I grew up with slide rules, and still have a Faber-Castell 152/82, but I got an HP-45 in 1975 and still rely on my 41CX every day.

[@ChaseNoStraighter]

In 1972 I picked a circular slide rule because it fit in my pocket. There was only on kid who could afford the HP-35.

[@subjectt.change6599]

Just found the channel. Got into slide rules through my Dad, a retired operating engineer in the petroleum industry, and amateur aviator. He gifted me his SP Precision “Sterling Slide Rule” and a Citizen Skyhawk AT chronograph. My wife got me my Citizen Promaster Nighthawk, which is my favorite C&D scale slide rule. Question: given your love of the technology, why don’t you wear a slide rule watch? I know they’re not terribly practical, but what a conversation piece, and great fiddle toy!

[@ProfessorHerning]

Thanks! I hope I have time to put more content up soon. I have thought about getting a watch with a slide rule bezel before. They tend to be expensive, though, and I have a bit of a utilitarian preference in watches: I like them simple and not too large. I think if I had a watch with a bezel I'd probably want a timer bezel because I might make use of it when cooking, etc. In most of the videos I'm wearing a Seiko 5 automatic field watch (mechanical, self-winding). I wore through a couple of those -- they tend to last about 5 years before they become impossible to regulate in my experience. I switched to a similar-looking Seiko solar watch and I can't say I miss having to set the time every few days! Tangential story about my math students: I love watches with an analogue face because of the spatial/visual sense of time they impart, but I think this preference is on the decline, if not gone already, among the younger crowd. During tests I used to project a big analogue clock on our classroom's digital projector so students could easily see how much time they had left. I guess I assumed they, like me, preferred the analogue face. In recent years, more and more students have said they have trouble telling how much time is left, so I switched to a digital countdown timer.

[@subjectt.change6599]

All very good points. Love the channel! Just a huge geek for analog tech of any kind. Any chance of your digging up some specialty or esoteric slide rules to demonstrate?

[@subjectt.change6599]

And just my two cents; this 33 year old math student benefits greatly from slide rules and analog clocks. Being able to visualize what’s happening in the operation is very helpful what with my dyscalculia. I’m not saying ditch the digital; but if you encounter students who struggle with “getting it” (algebra looks like mystic runes to a dyscalculic) try turning them on to slide rules. They may still end up majoring in philosophy, but at least they won’t resent mathematics. Also Martin Gardner taught me to LOVE math.

[@ProfessorHerning]

I will try, as I collect them. At the moment I have mostly general purpose/engineering slide rules. Have you seen the videos on the Hemmi 153?

[@ProfessorHerning]

I do bring slide rules to class and show off the basics, but I don't spend a lot of time on it. I'd love to do more, but I'd probably get in trouble. With the clocks, it's like a lot of other things in teaching entry level college classes: you have to walk a line between meeting them where they are, potentially under-challenging them, and trying to accomplish too many things in one semester.

[@daveduncan2748]

For those that don't use RPN, they don't know what they are missing. First thing I do when I get a new computer or phone is install an RPN calculator on it. In my first engineering class in college (Statics), I saw people using those crazy RPN calcs and I had this fancy algebraic TI calc. I felt sorry for them. Then I once asked a few of them why they were bothering with those dinosaurs, when "new" calculators were so impressive. They were patient with me and did a couple of the homework calcs side by side with me. They did them about 5x faster than me, and with fewer errors. Plus, they didn't have to enter parentheses, and check that they were all matched up. I went and bought an RPN calculator (HP41cx) and never looked back. My only regret is that sometime in the personal computer era I threw away that calculator. I have an HP41 on my phone, but it's not as good as having those tactile keys!

[@daveduncan2748]

@@colinsouthern I downloaded the Prime app, and played with it a few months ago. But I haven't really grokked it yet, and so I still go to the 41 app for quick calcs. Maybe I need to watch some tutorials on using the Prime.

[@daveduncan2748]

@@colinsouthern Just tried the deep stack capability, and I see how that is better than the four level stack and single line display of the 41c. I'll put that apps beside each other and try to get used to the Prime. Maybe I'll even check out the Kindle book. Thanks for the tip!

[@daveduncan2748]

@@colinsouthern No. You are wrong. I don't HAVE to argue with you! I just WANT to. ;-) Seriously, it sounds like we may have a similar programming history--and age. Yes, after my experimenting, I had to guess that the CAS button meant Clear All Screen or something. And it did!

[@cigmorfil4101]

RPN calculators are much-much easier to code the expression parser for than algebraic calculators. With RPN you only need to ensure you have enough numbers on the stack when an operator comes along, whereas with algebraic you need to consider the priority of operators, and stacking the result so far if necessary.

[@Mikael5732]

Enjoyed the video. Thanks.

[@art6268]

You do have sort of a "second button". The "arc" button modifies the trigonometric functions.

[@okaro6595]

Parenthesis were in general introduced the late 70s. First non-RPN scientific calculators calculated strictly from left to right with no precedence for multiplication just like four function calculators so still. Casio fx-39 from 1978 was among the first to have precedence and parenthesis. I had it in school.

[@ProfessorHerning]

The TI SR-50 from early 1974 doesn't have parentheses but it does prioritize multiplication over addition (using an internal stack). In fact, a lot of early calculators with parentheses don't do this either. Once TI added parenthesis it set the standard calculation model for non-HP scientific calculators for over 10 years. Yes, Casio eventually copied and popularized it, but I don't think it was their idea.

[@ProfessorHerning]

Looks like 1975's TI SR-52 might be the first such calculator (with the popular TI-30 being introduced in '76). The fx-39 isn't out for a couple more years, I believe, and its predecessor, the fx-29 doesn't have either feature (precedence, parentheses). It was definitely a period of fast development. I do give credit to TI for realizing that some alternative to RPN entry is really useful, unlike other early competitors. Once everyone realized it was a pain to neither have RPN nor precedence with parentheses, (almost) everyone copied TI's system.

[@aliensoup2420]

Seems to me that if you are performing a long string of decimal calculations, the calculator is better since it maintains precision and reduces rounding error. But in practical use, most realistic calculations depend on the least significant digit for accuracy. Most measurements aren't more precise than a slide rule provides, so it seems the slide rule is sufficient, but the calculator is faster.

[@johnchestnut5340]

That depends upon the calculation. Some calculations are faster on a slide rule. It takes more time to enter a bunch of key strokes. But generally the calculator/human combination is faster.

[@karhukivi]

The big advantage of a slide ruler, apart from not needing batteries, was that you had to keep evaluating the intermediate results in your head. This gave an intuitive feel for the order of magnitude of the result. Calculators give too many digits and a false sense of precision. A Quaternary geologist I was working with was weighing gravel and sand fractions for a sieve analysis and he divided 210 grams by 1550 grams and declared the percentage was 13.54839% A slide rule would have given a more realistic 13.5%

[@yopappy6599]

I know, pointing out the 10 digits after 76.2, but in the end you only need 76.2, so why does it matter? I remember seeing my grandpa use a slide rule sometimes, even in the 90s. 😂 He was a ET in the CG, MCPO. Even worked for NASA during the successful Apollo missions. I admittedly, have no clue how to use one, even after the video. 😂

[@karhukivi]

@@yopappy6599 Pilots use them all the time, also foresters as the wet environment is not good for electronic calculators. I have one for wire gauges, but they are fun gadgets to play with. A pity he didn't have time to show you how to use one. Stay safe!

[@okaro6595]

Modern calculators have gotten worse in this. You enter the formula and a result pops out. On earlier ones you saw the intermediate results which helped detecting errors. Sure the line entry does also have also benefits.

[@robertromero8692]

Any good engineer knows about limited precision. Test choices NEVER give answers to a lot of digits.

[@karhukivi]

@@robertromero8692 Engineers and physicists are practical people and understand precision and accuracy. However, some scientists are seduced by the imaginary "precision" of a lot of decimal places - they seem to think it looks very important!

[@oundhakar]

You ought to have calculated the error. It's amazing that you can get results to within 0.5% with the slide rule!

[@raymondfrye5017]

How did you obtain this result?...0.5%?

[@allswellinendwell6957]

Considering your significant figures, both produced the same and correct answer. The HP may report to a higher precision, but it's calculated, and not real. But the real benefit of all those digits of precision, is that when you have significant figures past the usual 2 or 3, you can calculate to those significant figures without loss of precision. Alas, it's a pet peeve of mine that many STEM people have loss the art of correctly reporting significant figures.

[@chef1arjunaidi]

I am an HP calculator fan. I have respect for the slide rules. Remember that many of the USA's high tech such the bomber aircraft, early nuclear submarines and the early space rockets were calculated by engineers with slide rules

[@MrWaalkman]

Anyone else remember the "Pi wars" between the HP and TI crowds? :)

[@miholju]

Do much collateral damage in such a war.

[@MrWaalkman]

@@miholju Mostly just a bunch of yelling. Just a difference of +/- 2.667641894049666e-7.

[@pietergeerkens6324]

Consensus among HP fans was that the 0.3 second saved 50 or 60 times on an exam was undoubtedly the difference between a PASS or FAIL grade. For example, on an (RPN) HP calculator one enters 4, 5, 2 - - instead of: 4 - ( 5 - 2 ) = where "," stands for the button. Note that RPN notation requires one less button push (ie 7 instead of 8). All those saved 1/3 second add up over a long exam. ;-)

[@peterwiles1299]

Still have my HP35 and periodically use it. And still have my sliderule, but it’s parked up in its box somewhere.