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Subject: Cube Root

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Jack-Iowa    Posted 01-11-2019 at 08:05:01 [URL] [DELETE]        [Reply] [Email]  
  • Cube Root
  • Way back in Algebra class we were taught how to take the Cube Root of a number long hand!

    I have long since forgotten how to do it as have my classmates. Even asked the teacher some years back. She had aged and did not remember it either.

    Did anyone else learn this? Do you still remember it?

    Jack

    Tim Daley(MI)    Posted 01-12-2019 at 08:28:41 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Cube Root
  • They don't teach much in US schools anymore, having pretty much discarded US History, technical math, and gym class. It all has to be computer related, learning Spanish and/or Chinese. Here's one for ya'll. Ask a college engineering kid what a slide rule is and if he knows ask if he can use it.

    Tim Daley(MI)

    Jack - Iowa    Posted 01-12-2019 at 08:46:37 [URL] [DELETE]        [Reply] [Email]  
  • Re: Cube Root
  • Thanks Tim,

    Of course what you say is too true but at least you gave me a chuckle for today! Afraid my slide rule is stored in the garage but at least I do know where it is.

    I have to admit I'm impressed with the amount of knowledge my oldest granddaughter gleaned out of school. Much more than I had out of high school. She also studied Japanese and now, having finished college, is teaching English in Japan. Long ways away! Her eventually goal is medical school after she finishes "having some fun".

    Jack

    Tim Daley(MI)    Posted 01-12-2019 at 10:58:16 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Cube Root
  • Back in the mid 70's, the company I was working for had purchased a Pratt & Whitney STAR-TURN NC Lathe to add to the Warner & Swasey two NC Turret Lathes we already had. I was the department supervisor/programmer/process engineer so had to teach myself and a few others, the boss for one, all about it. GENERAL NUMERIC/FANUC were relatively new to the NC machine tool industry and in 1975 the transition was underway from NC Machining to CNC Machining. FANUC would be the world leader by the 80's. We were one of two US companies who had a new P&W NC Lathe and so the Japanese had sent a technician over with a basic 12 page operation manual. It was assumed one already knew G-Code programming. the tech spent two weeks with me as I translated things for him so he could write and put in the soon to be published in English technical manuals for the machine and control. It was funny to see how they write just - like they talk with broken English. Some of it translated into the manuals as well. In the 70's and early 80's it was all about competing with the wily Japanese. In the mid-1980's it now included Germany too so if you had language skills in Japanese and German, you were one up in the industry. This was the birth of the new world-class global economy system. Toyota came to the US in the early 70's to observe GM production and then went back and made Dr. Demming their mfg god and made cars a lot better. The Germans always were tops in engineering. My last company as Manufacturing Process Engineer took me to the BMW company where the new young Indian engineers were double and triple tolerancing dimensions -many details were grind finish tolerances needlessly. You can have all the paper degrees in the world but if you have no hands-on, real-life world experience, they don't mean a thing.

    Tim Daley(MI)

    Jack - Iowa    Posted 01-13-2019 at 19:20:40 [URL] [DELETE]        [Reply] [Email]  
  • Re: Cube Root
  • About that same time I was working for a small custom manufacturer in the St. Louis area. Supervising the electronic production and filling in as a Electronic Engineer.

    We received a new machine, Either a riveter or a punch press and it fell to me to set it up. Opened the manual and was faced with an adjustment, the measurement of which was given in 4 decimals. I had nothing I could measure that accurately with.

    Happened to take another look at the name plate and found it was manufactured in Italy.

    The light bulb lite and I realized it was converted metric. Did the reverse conversion, grabbed my pocket scale and set the machine up!

    On a side note: All of the talk in Washington about the Chinese stealing technology. What's new? We built two machines which ended up going to China and were no doubt copied many times. One was a multi-head spiraller for manufacturing resistors, the other a bottle inspector machine. I left that job in 1977 after 11 years there.

    wer-fl    Posted 01-11-2019 at 23:09:17 [URL] [DELETE]        [Reply] [Email]  
  • Re: Cube Root
  • Way before calculators my Great Grandmother taught me how to do long hand cube root or square roots. Say you were to determine the cube root of 46656. You start by dividing by 2 if possible, and continue, then 3, then 4 etc.
    2(46656)
    2(23328)
    2(11664)
    2(5832)
    2(2916)
    2(1458)
    3(729)
    3(243)
    3(81)
    3(9)
    3(3)
    3(1)
    Then for cube root groups of 3 roots or 2 X 2 X 3 X 3 = 36
    QED

    Jack - Iowa    Posted 01-12-2019 at 07:51:31 [URL] [DELETE]        [Reply] [Email]  
  • Re: Cube Root
  • Certainly a different method! Looks like it works also.

    Thanks for posting.

    Paul in MA    Posted 01-11-2019 at 17:26:49 [URL] [DELETE]        [Reply] [Email]  
  • Re: Cube Root
  • I've had to use sq root a couple times working with Right Triangles, but I can't remember ever needing to find the cube root of something outside of a classroom.

    Tim Daley(MI)    Posted 01-13-2019 at 07:25:19 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Cube Root
  • I could do trig in my head, still can do some things. As a CNC Programmer/Engineer, writing programs was second nature to me. Many times via MDI right at the machine. G-Code programs were always written in absolute values, no ATNRC. Angles not only had to be trigged out, then using tool nose radius compensation values, had to be calculated in as well. Ditto for generating arcs and partial arcs. The latter was the hardest to do and always involved pencil and paper; I learned long before IBM had PC's on every desk and Apple was something you gave the teacher. Gates, Wozniak, and Jobs were still smoking weed in college when I learned NC Machining. Today, the term "CNC Programmer" is a misnomer as these kids all think using a CAD/CAM program is what it is all about and have no clue. MasterCam™ and the like only spit out what you spit in. If you don't know G-Code and tooling, any wrong data input will result in a mucked up program and finished part. If you don't have a basic machining background, you have no clue what feed and speed are all about. Now, today, I would not hesitate to use a CAD/CAM software to generate a G-Code program on any 3-D milling job. The cost of scrapping out a huge piece of aluminum, steel, or even plutonium cannot be accepted. I'm just saying if you've never had to calculate out and write an NC program long hand, you are not in the same league. Quick: TAN 30° x .06?

    Tim Daley(MI)

    Tim Daley(MI)

    Jack - Iowa    Posted 01-11-2019 at 17:35:21 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Cube Root
  • I agree. I've used square root many times. Never Cube root. However it's a memory think. I'd like to retain a small part of it.

    Paul in MA    Posted 01-11-2019 at 18:03:17 [URL] [DELETE]        [Reply] [Email]  
  • Re: Cube Root
  • We had a couple demolition formulas in the Army where we had to calculate the cube of the blast radius but never the cube root.

    steveVa    Posted 01-11-2019 at 11:29:13 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Cube Root
  • The cube root of 10 is 2.16.

    Jack    Posted 01-12-2019 at 20:20:38 [URL] [DELETE]        [Reply] [Email]  
  • Re: Cube Root
  • Not quite Steve. Cube 2.16 and you will get 10.077696

    2.15443469003189 is closer but yields 10 with a 1 in the 13th place to the right of the decimal sign. Excel will not allow me to go any more digits.

    Life is fun!

    Jack

    SteveVa    Posted 01-13-2019 at 14:20:20 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Cube Root
  • Hey Jack,
    Have you ever used the cube root for anything? Anything?
    For my use rounding to two digits is enough.
    I found that by taking a random number and multiplying by it self three times. Thjen just interpolate. Or use ratios.
    Takes about a minute. Works great.

    Jack - Iowa    Posted 01-13-2019 at 15:30:09 [URL] [DELETE]        [Reply] [Email]  
  • Re: Cube Root
  • Steve, can't say I have but that may be because my memory is so bad. After all I'm only 88! There is still time.

    Jack

    steveVa    Posted 01-13-2019 at 19:07:34 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Cube Root
  • Not here either. I have been in the architecture and building business for 40 years and have yet to use a cube root or any of the calculas they made me take. I have however used pie are square and a square plus b square equals c square... lol..
    But like you say there is still time.

    John in Mich    Posted 01-14-2019 at 18:32:56 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Cube Root
  • For fun I took Tim Daley comment above and sent the question to my Granddaughter. She is a Junior at Central Michigan University in Meteorology with a minor in Mathematics. I'm waiting to get a reaction. LOL Grandpas can be develish. Just ask her.

    poderac    Posted 01-11-2019 at 08:34:42 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Cube Root
  • https://www.wikihow.com/Calculate-Cube-Root-by-Hand

    Jack - Iowa    Posted 01-11-2019 at 15:02:29 [URL] [DELETE]        [Reply] [Email]  
  • Re: Cube Root
  • That may well be the method I was taught. Very similar at least. Last time I looked I found a method but it was not the one I was taught.

    Jack

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