Ummm… Houston, we have a problem…

This… THIS is why you should use an actual calculator, or even better, a slipstick to do math, if you don’t have pencil and paper handy…


TBT… — 36 Comments

  1. Order of operations. They’re both right, but with different OOO stacks.

    When it matters, specify with parenthesis.

      • That is my thought too – 3 x 3 = 9. How does the calculator figure it as 1 ?

        I’m an idiot in math (self admitted), so my apologies if asking how this works is needed.

        • It’s figuring 6/2*3=>6/6=1, when it’s really 6/2*3=>3*3=9

          Order of operations (PEMDAS) stipulates that you solve the equations in the parenthesis first, then exponents, and then multiply and divide from left to right, then add and subtract from left to right.

          • PEMDAS is actually a recently formalize way of doing it.

            The problem is the symbiology for the equations between two different methods of determining the order of operations is identical. This means there’s no way to determine what the equation is trying to solve or which order of operations is intended.

            The best you can hope for is to find out which method of solving the equation your electronic device is using and then construct your equations using THAT order of operation.

          • I never heard of PEMDAS. But in the IT world, we refer to PEBCAK.

  2. Lordy, I haven’t heard about a slide ruler in years. I wasn’t sure they even made them anymore. Yep! $110 on Amazon (including scabbard).

    • A hunnert ten dollars ? Yow ! I bought a Pickett & Eckel Model 600 ES for eight bucks at the local flea market, complete with cool leather original pocket cover (intended to use the cover as a knife sheath but relented). Everything works fine.

      Now I just have to learn how to use it – first question – where do you plug it in …

  3. I’ve always wanted to hand some kid a slide rule and watch him try to measure things with it.

  4. “Order Of Operations” is merely a convention to make an equation resemble a real world problem that needs to be solved.
    Math isn’t REALLY about equations.
    It’s REALLY about determining how many bricks you need to build a house, or how many pies you need to feed the family at Christmas, or how much fuel you need to to land on Mars and return. The parentheses and brackets and right-to-left are ONLY organizational tricks that make sure everybody gets a six-ounce piece of cherry pie, and not 1/64 of a cherry.
    They don’t teach it that way, though, because education is really a gang initiation, and they don’t want to let the unworthy come in.
    They might start to assume they are invited to conventions, or something else of that egregious nature.

    • What he said!

      Pat’s answer is also a good way to test to see if someone is in theoretical or applied science.

    • With the leftward shift of our education system, math is now about inequalities. 😛

  5. Abacus. It’s the way. But if it were talking about ice cream, I would go with the 9. Just saying.

  6. That Reverse Polish Notation will get you every time — the very first hand calculator I had — a very nice HP — back in 1975 had that. Took a little getting used to, but worked well once you got the hang of it.

    • RPN for the win! I still use my old HP. It still works fine, mumbledy decades, er, I mean years later.

  7. Slide rules don’t do addition.

    I still have a couple of cheap plastic slide rules that I used to know how to use.

    Just to be different I took it to the testing session for my HAM radio license. They are still listed along with calculators as items you can use during the test.

    I was bored in a high school math class back in the 1970’s and the teacher handed me a slide rule and an old math book and told to figure how how to use it, I did.

    • Some slide rules do addition – it’s a simple linear function.

      My first one had two separate slip sticks, a hairline slide, and was double sided. It did addition and trigonometry in addition to the usual functions. My idiotic parents threw it away while I was serving overseas.

  8. OH BOY… Just tried this on my Iphone and got completely different result…

  9. You can tell I’m not a math major. It took me about 45 seconds to figure out why they were different.

    I prefer a mechanical E-6B to the electronic ones. No batteries, they get you within a reasonable exactitude, and with the large “instructor-sized” aluminum ones, they double as a student attention grabber when applied lightly to the cranium of a day-dreaming ground-school attendee. (Or so I was told.)

    • The E6-B also requires knowing the steps to solve for a given problem. The electronic version only requires button pushing. And if one inputs an error they may have to start over whereas with the mechanical that is not necessary. And the mechanical is truly one handed operation.

      I love my mechanical cordless, never needs batteries E6-B. And I still use other slide rules. I never heard ’em called a slip stick. That’s a good one.

  10. Yup. PEMDAS. I nearly aced the math portion of the GRE. Haven’t used it since.

  11. My Son-in-Law, a Scientist, was visiting recently & we were looking thru some drawers in the basement for something, maybe an old baseball glove. We ran across my old slide rule w/scabbard. He was amazed, he’d never seen one. When I tried to demonstrate how it worked I realized it’s been 50 years 🙂

    • Slide rules don’t need batteries, they work in bright daylight, and don’t break if you drop them.

      I still have mine… admittedly I haven’t used it in thirty years, and I’d have to dig waaay back into the dusty corners of the meatware to remember how to use it again, but it will always work.

      One of these days I’m going to make a little wooden box for it, with a glass front and a brass hammer hanging on a chain. The sign will say, “IN CASE OF EMERGENCY, BREAK GLASS.”

      • lol! GMTA! I did this with an abacus as a gift for my dad.

  12. All- Thanks for the comments. Yes, in the old days of slide rule is also known as a slipstick. EA6-Bs and the military version were known as whiz wheels, and were operated with one hand. There was also an assumption in those days that you understood the underlying math mind what you were trying to do.

    Posted from my iPhone.

  13. The first electronic calculator that I saw in the wild was in Chemistry 101.
    The professor was a Deutschephile and as a lover of organization insisted on an alphabetical seating arrangement.
    To my utter amazement I ended up setting next to Ron with whom I had attended high school. Ron was a couple of grades ahead of me.
    The source of my amazement was that Ron had been accepted to Annapolis out of high school and I was surprised to find him “home” instead in Maryland singing “Anchors Away.”

    He explained: The Tet Offense of ’68 had decimated (as in one-tenth removed) the ranks of junior grade officers. So, the Navy did a “shake and bake” and Ron ended up in a hot LZ in The Land of Bad Things.
    They used the same LZ for exilfil as they had for infil.
    They came under mortar fire and Ron took a piece of schrapnel in the left side. A VC butt stroked him right on top of the schrapnel wound and Ron went down.
    The VC reversed his rifle to bayonet Ron, but one of his buddies shot the VC and put him down. Ron was thrown on the chopper and medivacted out.

    He was medically discharged and the VA was not only paying for his education, but bought him a shiney new, transistor radio-sized, electronic calculator.

    Thus, electronic calculators always, a least briefly, remind me of Ron and his electronic calculator.

    BTW: if 1/1= 0.111111 ad infintum
    2/2= 0.222222 ad infintum
    3/3= 0.333333 ad infintum
    and so on.
    Why does 9/9= 1 instead of 0.999999 ad infintum?

    • You’re math is wrong. All of those equal one. Any number divided by itself equals one. Non-mathematically, if you have eight nickels sitting in a pile, and they must be divided equally among eight people, each gets one nickel.

      On the other hand, 1/3 = 0.333333 ad infintum, 3/3 = 1, but 3 * 0.333333 = 0.999999 ad infintum. This is simply due to limits in representing a fraction as a decimal, not to a quirk in actual math. 1/3 * 3 = 1, after all.

  14. Waepn- Yep, lots of that going around back then. My first one was a HP-47, I think I paid $400 for it.

  15. Aha, yes, order of operation issue. neatly solved (avoided) by using a stack machine: RPN. The thing I use most is on my phone: it’s an emulated HP-48.

  16. I was given a slide rule for my 12th birthday in 1965. I figured out how easy it was to make it add and subtract, but that’s as far as I got. Too bad; my stepfather was a pilot, and had an instrument case weighing 7 metric tons filled with circular slipsticks and charts and things that I had to load into the car for him whenever he had a trip. To this day, I don’t know how to use a log table, although I DID have a chemistry teacher try to explain it to me in 1976 when the batteries died right before a test. Back then, science textbooks had log tables as appendices, and (advanced) psych textbooks had random number tables, along with ‘p’ and ‘t’ values.

  17. Since I knew the proper order of operation on my phone I wrote as (2+1)2 div 6=1

  18. I had several slipsticks back in highschool. The big one had something like 22 scales on it (2 sides). Way overkill for me. I think I still have them, after 50yrs.

  19. Back on — I still have a couple of sliderules… somewhere. One of the problems they solved rather neatly was avoiding people use more precision than their initial data allowed for.
    And log tables… one job I had, a very long time ago, involved calculating the guidance for very very long range weapons (which was then punched into a paper tape and loaded into the missile –really). For which task we needed some serious accuracy in some messy arithmetic. We had a shelf full of seven place log table for number and trig functions… and a Friden calculator (it even took square roots, given enough time) to do the arithmetic.
    Those were the days!