Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Calculators TI-30X Pro - Decimals Rounding issue

  1. Apr 16, 2018 #1
    Hi guys,
    I am using a Texas Instruments TI-30X Pro calculator.
    I add 599,944,263.55 to 8,404,167.32 and get 608,348,430.9 instead of 608,348,430.87. It seems it rounds the decimals on its own.
    What am I missing?

    Thanks i advance for your answers and help!
     
  2. jcsd
  3. Apr 16, 2018 #2

    DrClaude

    User Avatar

    Staff: Mentor

    Isn't the display limited to 10 digits? In that case, then it will indeed round the result to 10 digits.
     
  4. Apr 16, 2018 #3
    Thank you for your reply.
    Now I quote from the User Manual that came with the product:

    [poly solv] An entry or menu displays beyond 16 digits.

    I asume it should display the result without rounding it.

    I guess the limit in digits display goes beyond the 10 digit you normally find in so called market calculators.
     
  5. Apr 16, 2018 #4

    DrClaude

    User Avatar

    Staff: Mentor

    What is the answer to ##\sqrt{3}##?
     
  6. Apr 16, 2018 #5
    1.732050808
     
  7. Apr 16, 2018 #6

    DrClaude

    User Avatar

    Staff: Mentor

    So the calculator is indeed rounding to 10 digits (##\sqrt{3} = 1.732\,050\,807\,568\,877\ldots##)
     
  8. Apr 16, 2018 #7
    Then in my hundreds of millions arithmetic I should get Syntax Error or similar error considering the, I quote:

    EQUATION LENGTH ERROR — An entry exceeds the digit
    limits (80 for stat entries or 47 for constant entries); for
    example, combining an entry with a constant that exceeds the
    limit.


    I am confident I am doing something wrong. I tried the same calculation on a Chinese simple calculator and it works perfectly fine. The price and brand comparison is no match and not the subject to my inquiry.
     
  9. Apr 16, 2018 #8
    But probably you are right and the producer missed filling the "10 digit limit" information in the User's Manual.
     
  10. Apr 16, 2018 #9

    DrClaude

    User Avatar

    Staff: Mentor

    Internally, the calculator is probably keeping more digits than the 10. After having got the result for ##\sqrt{3}##, you can multiply it by 2, and you will probably find a number ending in 5, not in 6.
    I am not sure what you are doing, but it looks like you are entering something that is too long. Check what you are actually typing on the keypad.
     
  11. Apr 16, 2018 #10
    I quote from the User Manual:
    EQUATION LENGTH ERROR — An entry exceeds the digit
    limits (80 for stat entries or 47 for constant entries); for
    example, combining an entry with a constant that exceeds the
    limit.

    It should display pass by the 10 digit limit, shouldn't it? Instead it rounds it.
     
  12. Apr 16, 2018 #11

    DrClaude

    User Avatar

    Staff: Mentor

    The way I read, is that if you try to enter a constant with more than 47 digits, it will not take it. I would be extremely surprised if the calculator could actual do calculations on a 47-digit number. My guess is that internally, it must use 12-16 digits at most.
     
  13. Apr 16, 2018 #12

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2017 Award

    It uses 13 digits internally and displays 10.
     
  14. Apr 17, 2018 #13
    Thank you guys! I need a new calculator then.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted