ROUNDING NUMBERS

In most cases the results of calculations must be rounded to the correct number of significant digits. Follow the rules below for rounding numbers.

  1. When the first digit of those to be removed is less than 5, make no changes in the remaining number.

    2. Ex. 12.33 rounded to 3 significant digits = 12.3

    438, 829 rounded to 4 significant digits = 438,800

  2. When the first digit of those to be removed is greater than 5, drop all digits to be removed and make the last remaining digit one unit larger.

    3. Ex. 20.147 rounded to 4 sig figs = 20.15

    2567.345 rounded to 3 sig figs = 2570

  3. If only one digit is to be removed and that digit is a 5 , make the last digit of the remaining numbers an EVEN NUMBER.

Ex. 21.15 rounded to 3 sig figs = 21.2

21.25 rounded to 3 sig figs = 21.2

 

PRACTICE
  • Part A. Round all of the following to 2 sig figs.
    1. 11,124
    2. 137.98
    3. 0.0041245
    4. 4.45
    5. 77.5


  • Part B. Round all of the following to 3 sig figs.
    1. 1.25
    2. 1454.5
    3. 12.85
    4. 19.35
    5. 0.00469999