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Other Plugging numbers into my calculator wrong

  1. Feb 14, 2017 #1
    I'm getting pretty discouraged because I'm a straight A engineering student, but this semester I'm getting bad grades because I'm plugging things into my calculator wrong. I study a ton, and I definitely know the material, I just plug things into my calculator wrong and get the wrong answer.

    In my deforms class, we have one problem quizzes that are timed, and pretty much everyone struggles to even get the problem done in the given time. My professor said that he purposely gives us less time than we need to challenge us, so I don't have enough time to check my work because I'm literally rushing to finish a deform problem in 10 mins. This always results in me entering something into my calculator wrong, and getting the wrong answer.

    Most of my classmates don't have this problem, but I have always had it. Normally, my teachers see the mistake and only take off a few points as long as it's obvious that I knew what I was doing, but not this professor. I really don't know what to do lol, it's frustrating when you know the material, 99% of the work is correct, and you end up getting a 70 because the final answer is wrong.
  2. jcsd
  3. Feb 14, 2017 #2
    What do you mean by "plugging it into your calculator wrong"? You press the "+" symbol instead of "-"? Or what?
  4. Feb 14, 2017 #3
    Yeah, or I'll just type the wrong number on accident
  5. Feb 14, 2017 #4
    Just type things in more carefully. Look at the screen as you type to make sure the right numbers are popping up.
  6. Feb 14, 2017 #5


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    So interesting! In most of the scientific courses I have had (none of Engineering), when we analyzed and setup the problem solution correctly, we were given most of the problem item's credit. I believe that engineering is different in that the focus is on finding correct results.
  7. Feb 14, 2017 #6
    It's so frustrating. I understand that in real life you can't just be like "oops, I forgot a negative sign in my calculations, my bad!" whenever a rocket explodes, but in these instances, you have multiple people checking your work, and you are never so limited in time to where you can't take your time solving the problem that is given to you.
  8. Feb 14, 2017 #7
    It's hard when all you're trying to do is solve the problem before the time is up.
  9. Feb 14, 2017 #8
    It sounds as though you are performing much worse without being careful than you would if you took an extra five seconds (an overestimate, really) per problem to make sure you are hitting the right buttons.
  10. Feb 14, 2017 #9
    It definitely takes way more than 5 seconds
  11. Feb 14, 2017 #10


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    Actually, when the "rocket explodes" it's because:
    - someone was supposed to check your work, but didn't
    - someone did check your work, got a different, correct answer, but didn't have the confidence to speak up about it
    - someone tried to check your work and made the same mistake you made because it was a direct consequence of the checking procedure
    - someone checked your work, found you had the wrong answer, but left a note about it in a place that no one could see
    - someone checked your work, got a different answer, made a change on the rocket because of it, but that answer was also wrong
    - someone checked your work, caught a different error and fixed that error and assumed the rest was okay

    Anyway, you might want to look at this issue of "incorrect calculating under time stress" as an engineering problem to solve in and of itself. Some thoughts that could help:
    1. Can you do "back of the envelope" calculations in your head to estimate the approximate answer before you begin? This is a skill that comes with practice, but it might serve to help keep you on track.
    2. Is the issue with the calculator itself? Do you make as many mistakes with a different calculator?
    3. Can you save time on other aspects of the work? For example, would you save time by writing out your answer in point form or refining your style of showing your work so that you don't write down the trivial steps?
    4. Does studying more have any effect on the problem? You could be feeling the time crunch more because you need extra time to figure out a solution in the first place. As you get more experience, you'll get better at recognizing the path to a solution.
    5. Are there short cuts in the problems themselves that you could exploit to arrive a solution in a more timely manner?
  12. Feb 15, 2017 #11


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    Can you do prep before the exam and automate ie program your calculator so that some problems are just dumped into your calculator. You can learn a lot about a problem if you have to program a calculator to solve repetitive problems for you. I've had quizzes and timed exams where if I did not have a program or two in my calculator, I would have needed another 10-15 minutes to finish the calculations. And that 10 or 15 minutes would have been 5-10 minutes more that my time allowed.
    Also, you may consider using a different calculator, especially if your GPA is depending upon this. Some calculators are just not good for certain majors. An EE, ME or Physics major would be poorly served by a Ti-83/84. While switching calculators may be risky mid-semester, you might want to consider it.
    You do not specify which major you are in or if the class has calculator restrictions.
    Here is a list of calculators I would suggest in order of preference:
    Pocket scientifics:
    Ti-36 pro (cheap and conventional EOS, can hold equations on a stack)
    Hp 35s (fully programmable, 3x cost of Ti, RPN or EOS, but keyboard is optimized for RPN)
    Or a very cheap Ti-30x (AOS and no extra features, but is faster to use than EOS)
    EOS=Equation operating system (also called VPAM or DAL by Casio, although there are subtle differences)
    RPN=Reverse Polish Notation
    AOS=Algebraic Operating system
    I don't recommend Casio pocket calculators because some of their calculators lose their memories upon power off.
    Graphing Calculators:
    Ti-89 (suffers from lots of second functions and menus, so could be a bad call for timed quizzes)
    Ti-86 (actually better for number crunching, but discontinued, but fairly easy to find)
    Hp 50G (Discontinued and if you do not use RPN, not as good as above)
    I can't recommend anything else as other graphing calculators are not as well optimized as the above. Casio makes some good graphing calculators, but their actual features are not on par with any of the above. I cannot recommend a Ti-83/84 for any advanced math and it is missing some basic features too. These missing features can cost you time to crank out even simple work.
    Also, I would avoid the newest Ti Nspire, the Hp Prime or similar graphing calculators for this type of class. These types of calculators are math teaching tools and will actually hinder your cranking out numbers under a time constraint. Yeah, they're calculators, but they are designed to explore math and do not seem optimized for cranking out quizzes under duress.
  13. Feb 15, 2017 #12


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    What calculator are you using?
    A scientific calculator like the TI-8x?

    Can you give an explicit example of how you use your calculator?
    Do you take advantage of your calculator-memories/variables?
    Do you take advantage of your calculator's algebraic input?

    Often, I notice a lot of students work quite inefficiently (not using features of their calculator).

    For example, I'll STORE the value of the mass in "M", then use "M" everytime I need it.
    With values stored, I would write MV^2/2 [which looks like the physics] rather than try to enter numerical values.
    I would save intermediate calculations to memory locations
    so that I don't have to transcribe values (possibly incorrectly...
    or possibly introducing roundoff errors because I didn't record every digit of the display).
  14. Feb 15, 2017 #13


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    I'm sorry, but you just don't know what the real world is like. When you finish school and get an actual job they'll be putting reams of contrived questions on your desk every day. You'll have only a brief moment to answer each one, and precision use of a calculator under time pressure will be you one of your most valuable skills as an employee. When I interviewed at my current job they gave me a full page of arithmetic to punch into my calculator in just 90 seconds. I nailed it and got the job because I've been practicing with my TI-83 basically non-stop for 15 years. The guy who interviewed right after me accidentally made the same type-o on his calculator twice in a row. Can you believe it!? Twice in a row! A company security guard promptly came over and bonked him on the head, and then threw his body down a garbage chute.

    The real world is brutal man. Listen to your professors. You're learning crucial skills here.
  15. Feb 15, 2017 #14
    When I first started working, my supervisor (an immigrant from Cuba) took me aside and told me a long story about napoleon getting dressed by his butler; the point being "dress me slowly, I am in a hurry..."

    Good advice I have tried to remember. It sounds like maybe you have these one-question quizzes frequently. Next time, try to go just a little slower, as a kind of experiment.
  16. Feb 15, 2017 #15

    Vanadium 50

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    Have you ever heard the expression "If you go any faster we'll never finish"?
  17. Feb 15, 2017 #16
    "Slow down to speed up"
  18. Feb 16, 2017 #17
    Interestingly I have had a similar experience. When I was a grad student programmable desk top calculator were just be introduced. We were evaluating different manufacturers.. One particular model drove me crazy, I kept on making key stroke errors. All I could figure is that the key arrangement/location, touch or key size was somehow incompatible with my eye hand coordinating neuro network. I had no problem using the one we settled on. So trying different calculators may help.
  19. Feb 16, 2017 #18


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    That seems like bad advice, and not at all what the real world is like. What job were you interviewing for?
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