PhAST Track Mathematics Module: Revision: Significant Figures & Rounding

Rounding is useful, but if you round throughout a multiple-stage question, you will introduce error into your calculation:

You can see that by rounding to 2 decimal places (RHS), we have introduced just under 1% error to our result.

SO…to keep error to a minimum, ONLY round at the end of your working 

Round 13.0357169 as directed:

• 2 decimal places
• 4 decimal places
• 2 significant figures
• 3 significant figures
• 4 significant figures
• 6 significant figures

Significant figures (also called “sigfigs”), are used to reflect the accuracy of the information you are presenting.

Take this quiz to test your understanding of sig figs…

http://antoine.frostburg.edu/chem/senese/101/measurement/sigfig-quiz.shtml

Generally, report your result to the smallest number of significant figures used in the input data:

1. Identify the number of significant figures or decimal places required
2. Count :

• From the LEFT the number of required significant figures
• From the DECIMAL POINT the number of decimal places

3. If the next number to the RIGHT is:

• < 5, the last number remains the same and the remaining numbers to the right are discarded
• ≥ 5, the last number is increased by one and the remaining numbers to the right are discarded