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  • Perplex
    IB Math AIHL
    /
    Approximations & Error
    /

    Rounding Numbers

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    Exercises

    Key Skills

    Rounding Numbers

    Rounding Numbers

    Rounding, significant figures, decimal places

    Want a deeper conceptual understanding? Try our interactive lesson!

    Exercises

    No exercises available for this concept.

    Practice exam-style rounding numbers problems

    Key Skills

    Rounding rules
    SL Core 1.1

    There are standardized rules for how to approximate numerical values:

    • If the digit after the one being rounded off is LESS than ​5​ (​0,1,2,3,​ or ​4​), we round down.

    • If the digit after the one being rounded off is ​5​ OR MORE (​5,6,7,8,​ or ​9​), we round up.

      ​
      1.34∣5→1.35
      ​
      ​
      1.34∣4→1.34
      ​
    Significant figures
    SL Core 1.1

    A significant figure is any digit that is not a leading or trailing zero. To round off to a number of significant figures, count off the specified number of significant figures, then round based off of rounding rules (down if the next digit is less than ​5, up if the digit is ​5​ or more).

    problem image


    NOTE: Unless a question states otherwise, on IB exams, you are expected to give answers to 3 significant figures.