# Significant Figures

Significantly Yours…Identifying Significant Figures and Related Calculations

Significant figures are digits that have precision and confidence in a measured or reported value. They can be difficult to deal with but these foolproof rules can help you sort through the muddy waters of significance:

• Look for the zeros—they are your main problem.
• All nonzero integers are significant (1, 2, 3…9)
• Zeros between two sig figs are significant (1009)
• Zeros at the beginning or end of a number are not significant (09, 1000)
• Zeros are significant IF there is a decimal present and the zero follows a significant figure (0.90, 10.0, 11.20, 1.02)
• Scientific notation zeros are not significant (4.3 x 104)

Try some examples….

Ex. How many SF are in each of the following values?

0.60 → ? [Ans: 2]

1.34 → ? [Ans: 3]

4560 → ? [Ans: 3]

0.075 → ? [Ans: 2]

1.23 x 105→ ? [Ans: 3]

Calculations Using Significant Figures (SF):

(1) Multiplication/Division: Perform the operation and keep the same number of significant figures in the answer as are present in the number with the least number of significant figures.

Ex. 1000 x 5.67 = _______ [Ans: 6000, keep 1 SF]

Ex. 2.45 x 9.1= _______ [Ans: 22, keep 2 SF]

(2) Addition/Subtraction: Perform the operation and keep the same number of decimal places in the answer as are present in the number with the least number of decimal places.

Ex. 4.501 + 3.4= ______ [Ans: 7.9, keep 1 decimal place) 