VIEWS: 43 PAGES: 14

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```									Title: Significant Figures and
Rounding
Objective: I will be able to determine the amount
of significant figures when given a quantifiable
number and round appropriately.
Questions: What is significant figures and how do
I round?
Notes:
Significant Figures
Some digits in an number may be
exact while others may be uncertain,
so chemists have devised a way to
determine which digits are the most
significant.
Rule #1 – All numbers that are
not zero are always significant
Example:
-487 miles has 3 significant figures
-3.1478654 has 8 significant figures
Rule #2-Zeros appearing between
nonzero digits are significant

Examples:
40.7 lbs has 3 significant figures
87,009 lbs has 5 significant figures
Rule #3 – Zeros in front of non-
zeros digits are NOT significant
• Examples:
0.009587 m has 4 significant figures
0.0000009 m has 1 significant figure
Rule #4-Zeros at the end of a
number and to the right of a
decimal point are significant
• Examples:
– 85.00 g has 4 significant figures
– 9.0700 g has 5 significant figures
Rule #5 – Zeros at the end of a
number with no decimal may or
may not be significant, if there is
a decimal point at the end of all of
the zeros then the zeros are
significant .
-2000 m has 1 significant figure or has 4
significant figure depending on if the zeros
are place holders
-2000. m has 4 significant figures because of
the decimal point.
Rounding Rules
• Use only the 1st number to the right of the
last sig. fig. number to decide whether or
not to round.
•   Less than 5, do NOT round
•   More than 5, round the last sig. fig. up by 1
• When using a calculator wait until the
very end before rounding. Try to keep as
many digits in the calculator until you
come to the very end.
Multiplying and Dividing
are in the piece of data with the least
number of sig figs.

2.37 cm x 15.67 cm x 7.4 cm = 274.82046
(keep two sig figs) = 2.7 x 102 cm3
1. Keep the same number of decimal places

34.039 m + 0.24 m + 1.332 m + 12.7 m =
48.311 m
(keep one decimal place) = 48.3 m
Scientific Notation
• This is a number that has 1 digit left of the
decimal point.
– Example 3.4 x 103
Exponent: Positive or Negative?
• When convert expanded numbers into scientific
notation:
– If you move the decimal to the left the exponent
number is postive
– If you move the decimal to the right the exponent is
negative.
• When converting from scientific notation back to
expanded form:
– If you move the decimal to the right the exponent
number is negative
– If you move the decimal to the left the exponent is
positive.