Significant Figures September 20, 2006
Posted by ecknipp in Significant Figures.add a comment
Rules for Counting
Significant Figures
• Nonzero integers
always count as significant figures. 3456 has 4 sig figs
• Zeros
A. Leading zeros do not count as significant figures.
0.0486 has 3 sig figs
B. Captive zeros always count as significant figures.
16.07 has 4 sig figs.
C. Trailing zeros are significant only if the number contains a decimal point. 9.300 has 4 sig figs 9300 has 2 sig figs
Sig Fig Practice #1
How many significant figures in each of the following?
1.0070 m 5 sig figs
17.10 kg 4 sig figs
100,890 L 5 sig figs
3.29 x 103 s 3 sig figs
0.0054 cm 2 sig figs
3,200,000 2 sig figs
Rules for Significant Figures in Mathematical Operations
Multiplication and Division:
# of sig figs in the answer equals the number with
the least precise measurement (the measurement
with the least sig figs) used in the calculation.
6.38 x 2.0 = 12.76
13 (2 sig figs)
Sig Fig Practice #2
Calculation Calculator says: Sig Figs Answer
3.24 m x 7.0 m 22.68 m2 2 23 m2
100.0 g ÷ 23.7 cm3 4.219409283 g/cm3 3 4.22 g/cm3
0.02 cm x 2.371 cm 0.04742 cm2 1 0.05 cm2
710 m ÷ 3.0 s 236.6666667 m/s 2 240 m/s
1818.2 lb x 3.23 ft 5872.786 lb·ft 3 5870 lb·ft
1.030 g ÷ 2.87 mL 2.9561 g/mL 3 2.96 g/mL
Rules for Significant Figures in Mathematical Operations
Addition and Subtraction: The number of
decimal places in the answer equals the
number of decimal places in the least
precise measurement (measurement with
the least # of sig figs).
6.8 + 11.934 = 18.734 → 18.7 (3 sig figs)
Sig Fig Practice #3
Calculation Calculator says: Sig Figs Answer
3.24 m + 7.0 m 10.24 m 3 10.2 m
100.0 g – 23.73 g 76.27 g 3 76.3 g
0.02 cm + 2.371 cm 2.391 cm 3 2.39 cm
713.1 L – 3.872 L 709.228 L 4 709.2 L
1818.2 lb + 3.37 lb 1821.57 lb 4 1821.6 lb
2.030 mL – 1.870 mL 0.16 mL 3 0.160 mL
