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What is 3 digit arithmetic?

  1. Nov 7, 2011 #1
    what is 3(or i, where i=1,2,3,4......∞) digit arithmetic? is it just working with 3 decimals or 3 significant figures? or is it base 3 arithmetic?
  2. jcsd
  3. Nov 7, 2011 #2


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    The expression could mean anything.

    But if I heard someone say they could do 3 digit arithmetic, I would assume they could add subtract and multiply 3-digit numbers (100-999).
  4. Nov 7, 2011 #3
    the context was talking about floating point numbers and catastrophic cancellation in the quadratic equation.

    it said using 3 digit arithmetic:
    *subs in some numbers, 0.2, 100.9 etc into the quad equation and at the end rounds the entire number to 3 digits*

    am i right in assuming that all the numbers used to input had to be 3 decimals and then the final number had to be 3 digits?
    or does every number in the process have to be rounded to 3 decimals as the number is created? step by step?
  5. Nov 8, 2011 #4


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    Of course, any decent calculator or computer will carry 12 or more digits for its calculations. But just to give a simple example, that a human could calculate easily, of how cancellation happens, they are restricting to three digits. I don't see any difference between using three digits from the outset and rounding to three digits.
  6. Nov 8, 2011 #5


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    What? Of course there's a difference.
  7. Nov 8, 2011 #6


    Staff: Mentor

    Since the context is floating point arithmetic, my guess at what you're asking is that numbers are represented by a 3-digit mantissa and an exponent.

    Using the numbers you gave as examples, 0.2 would be 2.00 x 10-1 and 100.9 would be 1.01 x 102.

    If you want a better answer, you'll need to ask a question that is clearer.
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