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)