1. Significant Figures
Tell how well the measurement was made (helps towards Precision)
Significant figures in a measurement include the known digits plus one estimated digit

2. Counting Significant Figures
RULE 1. All non-zero digits in a measured number are significant. Only a zero could indicate that rounding occurred.
Number of Significant Figures
38.15 cm 4
5.6 ft 2
65.6 lb ___
m ___

3. Leading Zeros
RULE 2. Leading zeros in decimal numbers are NOT significant.
Number of Significant Figures
0.008 mm 1
oz 3
lb ____
mL ____

4. Sandwiched Zeros
RULE 3. Zeros between nonzero numbers are significant. (They can not be rounded unless they are on an end of a number.)
Number of Significant Figures
50.8 mm 3
2001 min 4
0.702 lb ____
m ____

5. Trailing Zeros 25,000. in. 5 200. yr 3 48,600. gal ____
RULE 4. Trailing zeros are always significant.
Number of Significant Figures
25,000. in. 5
200. yr 3
48,600. gal ____
25,005,000. g ____

6. Scientific Notation
In scientific notation, all coefficient numbers are significant.
2.50 X 10 has 3 significant figures. 3

7. Learning Check A. Which answers contain 3 significant figures?
1) ) ) 4760
B. All the zeros are significant in
1) ) ) x 103
C. 534,675 rounded to 3 significant figures is
1) ) 535, ) 5.35 x 105

8. Learning Check
In which set(s) do both numbers contain the same number of significant figures?
1) and 22.00
2) and 40
3) and 150,000.

9. Learning Check
State the number of significant figures in each of the following:
A m
B L
C g
D m
E. 2,080,000 bees

10. Rounding with Significant Figures
Count from the first significant figure on the left and round to that number.
Round to
2 significant figures:
2.89m =
2.99m =
3156m =
2.9m
3.0m
3200m

11. Round to 3 Significant Figures
87.073m = X 10 m = m = 9009m = X 10 m = m =
87.1m
4.36 X 10 m
0.0155m
9010m
1.78 X10 m
630.m 8 8 -3 -3