Significant Figures
SIG FIGS!!!!!!!
Importance of Sig figs
• Sig figs tell people the precision of a
value.
• Precision: how many times you can
achieve the same result. (dart and
#19 over and over)
• Accuracy: how close your value is to
the true value (dart and bulls-eye)
Rule #1
•
•
•
•
•
All real numbers are sig figs.
Ex. 1235 (4)
Ex. 4487558 (7)
Ex. .2257 (4)
Ex. 14.88597 (7)
Rule #2
• All zeros between real numbers are
sig figs.
• Ex. 2007 (4)
• Ex. 24.0559 (6)
• Ex. 800000000000000004.05 (20)
Rule #3
• All zeros behind a real number in
FRONT of a decimal are not sig figs.
• Ex. 5000 (1)
• Ex. 410 (2)
• Ex. 100000 (1)
Rule #4
• All zeros BEHIND the decimal and in
FRONT of a real number are not sig
figs.
• Ex. 0.0045 (2)
• Ex. 0.0000078 (2)
Rule #5
• All zeros BEHIND the decimal and
BEHIND a real number are sig figs.
• Ex. 0.22570 (5)
• Ex. 0.998700 (6)
• Ex. 45.10 (4)
• Ex. 0.004580 (tricky…the underlined
zeros do not follow this rule.. 4)
How many sig figs?
#1
• 5sf
#2
• 8sf
#3
• 6sf
#4
• 1sf
50069 (?)
50069.004 (?)
448.000 (?)
8000 (1)
Addition and subtraction
• When adding and subtracting—pay
attention to the number of digits
behind the decimal point.
• Lowest number wins!
• Ex. 12.005
3 digits behind
+ 1.01
2 digits behind
13.015 = 13.02 2 digits behind
Multiplication and division
• When multiplying and dividing, pay
attention to the total number of sig
figs in each value in the problem.
• Lowest number wins!
• Ex.
12.501
5 sig figs
x 0.23
2 sig figs
2.87523 = 2.9
only 2 sig figs