1. S IGNIFICANT FIGURES Essential Question: How are significant figures used in measurement?

2. S IGNIFICANT FIGURES Significant Figures: The accuracy of a physical measurement is properly indicated by the number of figures used to express the numerical measure. Conventionally, only those figures that are reasonably trustworthy are retained. These are called significant figures. Essential Question: How are significant figures used in measurement?

3. R ULES FOR IDENTIFYING SIGNIFICANT FIGURES 1) Any nonzero digit is a significant digit. Examples: 3.14 has three significant digits and 239.67 has five significant digits. 2) Zeros in between nonzero values are significant digits. Example: 20.4 has three significant digits. 3) Zeros to the left of the first nonzero digit are NOT significant. Example: 0.0012 has two significant digits. 4) For numbers with decimal points, zeros to the right of nonzero digits are significant. Example: Both 2.0 and 0.0020 have two significant digits. 5) For numbers without decimal points, zeros to the right of nonzero digits may or may not be significant. Example: 350 may have two or three significant digits. To avoid confusion, use a decimal point: 350. has three significant digits, 350 has two. Essential Question: How are significant figures used in measurement?

4. A DDITION AND S UBTRACTION For addition and subtraction, look at the decimal portion (i.e., to the right of the decimal point) of the numbers ONLY. Here is what to do: 1) Count the number of significant figures in the decimal portion of each number in the problem. (The digits to the left of the decimal place are not used to determine the number of decimal places in the final answer.) 2) Add or subtract in the normal fashion. 3) Round the answer to the LEAST number of places in the decimal portion of any number in the problem. Example: 5.146 + 5.29 = 10.44

5. M ULTIPLICATION AND D IVISION The following rule applies for multiplication and division: The LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer Example: 2.200001  2 = 4

6. CLOSING ACTIVITY TICKET OUT THE DOOR: Copy the following examples and identify the number of significant figures. Length of a page= 22.7 cm Thickness of a page = 0.011 cm Distance to the sun = 149,600,000 km Speed of light = 299,790 km/sec Essential Question: How are significant figures used in measurement?